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Text File | 1990-11-06 | 83.0 KB | 1,585 lines

SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) NNNNAAAAMMMMEEEE sh, rsh - shell, the standard/restricted command programming language SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS sssshhhh [ ----aaaacccceeeeffffhhhhiiiikkkknnnnmmmmrrrrssssttttuuuuvvvvxxxx0000 ] [ args ] rrrrsssshhhh [ ----aaaacccceeeeffffhhhhiiiikkkknnnnmmmmrrrrssssttttuuuuvvvvxxxx0000 ] [ args ] DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN _S_h is a command programming language that executes commands read from a terminal or a file. _R_s_h is a restricted version of the standard command interpreter _s_h; it is used to set up login names and execution environments whose capabilities are more controlled than those of the standard shell. See _I_n_v_o_c_a_t_i_o_n below for the meaning of arguments to the shell. DDDDeeeeffffiiiinnnniiiittttiiiioooonnnnssss A _b_l_a_n_k is a tab or a space. A _n_a_m_e is a sequence of letters, digits, or underscores beginning with a letter or underscore. A _p_a_r_a_m_e_t_e_r is a name, a digit, or any of the characters ****, @@@@, ####, ????, ----, $$$$, and !!!!. CCCCoooommmmmmmmaaaannnnddddssss A _s_i_m_p_l_e-_c_o_m_m_a_n_d is a sequence of non-blank _w_o_r_d_s separated by _b_l_a_n_k_s. The first word specifies the name of the command to be executed. Except as specified below, the remaining words are passed as arguments to the invoked command. The command name is passed as argument 0 (see _e_x_e_c(2)). The _v_a_l_u_e of a simple-command is its exit status if it terminates normally, or (octal) 200+_s_t_a_t_u_s if it terminates abnormally (see _s_i_g_n_a_l(2) for a list of status values). A _p_i_p_e_l_i_n_e is a sequence of one or more _c_o_m_m_a_n_d_s separated by |||| (or, for historical compatibility, by ^^^^). The standard output of each command but the last is connected by a _p_i_p_e(2) to the standard input of the next command. Each command is run as a separate process; the shell waits for the last command to terminate. The exit status of a pipeline is the exit status of the last command. A _l_i_s_t is a sequence of one or more pipelines separated by ;;;;, &&&&&&&&, or ||||||||, and optionally terminated by ;;;;. Of these three symbols, ;;;; has a lower precedence than that of &&&&&&&& and ||||||||. The symbols &&&&&&&& and |||||||| also have equal precedence. A semicolon (;;;;) causes sequential execution of the preceding pipeline. The symbol &&&&&&&& (||||||||) causes the _l_i_s_t following it to be executed only if the preceding pipeline returns a zero (non-zero) exit status. An arbitrary number of new-lines may appear in a _l_i_s_t, instead of semicolons, to delimit commands. A _c_o_m_m_a_n_d is either a simple-command or one of the Page 1 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) following. Unless otherwise stated, the value returned by a command is that of the last simple-command executed in the command. ffffoooorrrr _n_a_m_e [ iiiinnnn _w_o_r_d ... ] ddddoooo _l_i_s_t ddddoooonnnneeee Each time a ffffoooorrrr command is executed, _n_a_m_e is set to the next _w_o_r_d taken from the iiiinnnn _w_o_r_d list. If iiiinnnn _w_o_r_d ... is omitted, then the ffffoooorrrr command executes the ddddoooo _l_i_s_t once for each positional parameter that is set (see _P_a_r_a_m_e_t_e_r _S_u_b_s_t_i_t_u_t_i_o_n below). Execution ends when there are no more words in the list. ccccaaaasssseeee _w_o_r_d iiiinnnn [ _p_a_t_t_e_r_n [ | _p_a_t_t_e_r_n ] ... )))) _l_i_s_t ;;;;;;;; ] ... eeeessssaaaacccc A ccccaaaasssseeee command executes the _l_i_s_t associated with the first _p_a_t_t_e_r_n that matches _w_o_r_d. The form of the patterns is the same as that used for file-name generation (see _F_i_l_e _N_a_m_e _G_e_n_e_r_a_t_i_o_n) except that a slash, a leading dot, or a dot immediately following a slash need not be matched explicitly, and the match is case sensitive. iiiiffff _l_i_s_t tttthhhheeeennnn _l_i_s_t [ eeeelllliiiiffff _l_i_s_t tttthhhheeeennnn _l_i_s_t ] ... [ eeeellllsssseeee _l_i_s_t ] ffffiiii The _l_i_s_t following iiiiffff is executed and, if it returns a zero exit status, the _l_i_s_t following the first tttthhhheeeennnn is executed. Otherwise, the _l_i_s_t following eeeelllliiiiffff is executed and, if its value is zero, the _l_i_s_t following the next tttthhhheeeennnn is executed. Failing that, the eeeellllsssseeee _l_i_s_t is executed. If no eeeellllsssseeee _l_i_s_t or tttthhhheeeennnn _l_i_s_t is executed, then the iiiiffff command returns a zero exit status. wwwwhhhhiiiilllleeee _l_i_s_t ddddoooo _l_i_s_t ddddoooonnnneeee A wwwwhhhhiiiilllleeee command repeatedly executes the wwwwhhhhiiiilllleeee _l_i_s_t and, if the exit status of the last command in the list is zero, executes the ddddoooo _l_i_s_t; otherwise the loop terminates. If no commands in the ddddoooo _l_i_s_t are executed, then the wwwwhhhhiiiilllleeee command returns a zero exit status; uuuunnnnttttiiiillll may be used in place of wwwwhhhhiiiilllleeee to negate the loop termination test. ((((_l_i_s_t)))) Execute _l_i_s_t in a sub-shell. The shell creates a new environment in which to execute the _l_i_s_t, but does not fork a sub-shell as a Unix system would. The original environment is restored on completion. {{{{ _l_i_s_t;;;; }}}} _l_i_s_t is simply executed. _n_a_m_e (((()))) {{{{ _l_i_s_t;;;; }}}} Define a function which is referenced by _n_a_m_e. The body of the function is the _l_i_s_t of commands between {{{{ and }}}}. Execution of functions is described below (see _E_x_e_c_u_t_i_o_n). The following words are only recognized as the first word of a command and when not quoted: iiiiffff tttthhhheeeennnn eeeellllsssseeee eeeelllliiiiffff ffffiiii ccccaaaasssseeee eeeessssaaaacccc ffffoooorrrr wwwwhhhhiiiilllleeee uuuunnnnttttiiiillll ddddoooo ddddoooonnnneeee {{{{ }}}} Page 2 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) CCCCoooommmmmmmmeeeennnnttttssss A word beginning with #### causes that word and all the following characters up to a new-line to be ignored. TTTTiiiillllddddeeee SSSSuuuubbbbssssttttiiiittttuuuuttttiiiioooonnnn Each word is checked to see if it begins with an unquoted~~~~. If it is, the ~~~~ is replaced by the value of the HHHHOOOOMMMMEEEE parameter. CCCCoooommmmmmmmaaaannnndddd SSSSuuuubbbbssssttttiiiittttuuuuttttiiiioooonnnn The standard output from a command enclosed in parenthesis preceded by a dollar sign ($$$$(((())))), or in a pair of grave accents (````````) may be used as part or all of a word; trailing new-lines are removed. PPPPaaaarrrraaaammmmeeeetttteeeerrrr SSSSuuuubbbbssssttttiiiittttuuuuttttiiiioooonnnn The character $$$$ is used to introduce substitutable _p_a_r_a_m_e_t_e_r_s. There are two types of parameters, positional and keyword. If _p_a_r_a_m_e_t_e_r is a digit, it is a positional parameter. Positional parameters may be assigned values by sssseeeetttt. Keyword parameters (also known as variables) may be assigned values by writing: _n_a_m_e = _v_a_l_u_e [ _n_a_m_e = _v_a_l_u_e ] ... Pattern-matching is not performed on _v_a_l_u_e. There cannot be a function and a variable with the same _n_a_m_e. $$$${{{{_p_a_r_a_m_e_t_e_r}}}} The value, if any, of the _p_a_r_a_m_e_t_e_r is substituted. The braces are required only when _p_a_r_a_m_e_t_e_r is followed by a letter, digit, or underscore that is not to be interpreted as part of its name. If _p_a_r_a_m_e_t_e_r is **** or @@@@, all the positional parameters, starting with $$$$1111, are substituted (separated by spaces). Parameter $$$$0000 is set from argument zero when the shell is invoked. $$$${{{{####_p_a_r_a_m_e_t_e_r}}}} If _p_a_r_a_m_e_t_e_r is **** or @@@@, the number of positional parameters is substituted. Otherwise, the length of the value of the _p_a_r_a_m_e_t_e_r is substituted. $$$${{{{_p_a_r_a_m_e_t_e_r::::----_w_o_r_d}}}} If _p_a_r_a_m_e_t_e_r is set and is non-null, substitute its value; otherwise substitute _w_o_r_d. $$$${{{{_p_a_r_a_m_e_t_e_r::::====_w_o_r_d}}}} If _p_a_r_a_m_e_t_e_r is not set or is null set it to _w_o_r_d; the value of the parameter is substituted. Positional parameters may not be assigned to in this way. $$$${{{{_p_a_r_a_m_e_t_e_r::::????_w_o_r_d}}}} If _p_a_r_a_m_e_t_e_r is set and is non-null, substitute its value; otherwise, print _w_o_r_d and exit from the shell. If _w_o_r_d is omitted, the message ``parameter null or not set'' is printed. Page 3 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) $$$${{{{_p_a_r_a_m_e_t_e_r::::++++_w_o_r_d}}}} If _p_a_r_a_m_e_t_e_r is set and is non-null, substitute _w_o_r_d; otherwise substitute nothing. $$$${{{{_p_a_r_a_m_e_t_e_r####_p_a_t_t_e_r_n}}}} $$$${{{{_p_a_r_a_m_e_t_e_r########_p_a_t_t_e_r_n}}}} If the Shell _p_a_t_t_e_r_n matches the beginning of the value of _p_a_r_a_m_e_t_e_r, then the value of this substitution is the value of the _p_a_r_a_m_e_t_e_r with the matched portion deleted; otherwise the value of this _p_a_r_a_m_e_t_e_r is substituted. In the first form the smallest matching _p_a_t_t_e_r_n is deleted and in the latter form the largest matching _p_a_t_t_e_r_n is deleted. $$$${{{{_p_a_r_a_m_e_t_e_r%%%%_p_a_t_t_e_r_n}}}} $$$${{{{_p_a_r_a_m_e_t_e_r%%%%%%%%_p_a_t_t_e_r_n}}}} If the Shell _p_a_t_t_e_r_n matches the end of the value of _p_a_r_a_m_e_t_e_r, then the value of this substitution is the value of the _p_a_r_a_m_e_t_e_r with the matched portion deleted; otherwise the value of this _p_a_r_a_m_e_t_e_r is substituted. In the first form the smallest matching _p_a_t_t_e_r_n is deleted and in the latter form the largest matching _p_a_t_t_e_r_n is deleted. In the above, _w_o_r_d is not evaluated unless it is to be used as the substituted string, so that, in the following example, ppppwwwwdddd is executed only if dddd is not set or is null: echo ${d:-`pwd`} If the colon (::::) is omitted from the above expressions, the shell only checks whether _p_a_r_a_m_e_t_e_r is set or not (_I_t _i_s _n_o_t _c_l_e_a_r _w_h_a_t _t_h_i_s _m_e_a_n_s). The following parameters are automatically set by the shell: #### The number of positional parameters in decimal. ---- Flags supplied to the shell on invocation or by the sssseeeetttt command. ???? The decimal value returned by the last synchronously executed command. $$$$ The process number of this shell. !!!! The process number of the last background command invoked. ~~~~ The shell reserves all variables beginning with a ~~~~ for its own internal use and these variables cannot be accessed by the user. The following parameters are used by the shell: CCCCDDDDPPPPAAAATTTTHHHH The search path for the _c_d command. (Note that because a colon is used by MSDOS to indicate a drive, a semi-colon is used to separate the path names instead of a colon - this implies that the CDPATH variable must be set using single or double quotes to surround the value). CCCCOOOOMMMMSSSSPPPPEEEECCCC Page 4 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) When the shell has to process an MSDOS ._b_a_t file, it expects the file indicated by the value of this environment variable to be an executable program capable of processing the MSDOS ._b_a_t file. The program is invoked with the arguments ////cccc bbbbaaaatttt____ffffiiiilllleeee____nnnnaaaammmmeeee. EEEEXXXXTTTTEEEENNNNDDDDEEEEDDDD____LLLLIIIINNNNEEEE This parameter defines a file containing a list of command which can accept an Extended Command Line using the indirect command file character @@@@. When a command which can process the Extended Command Line finds a parameter starting with a @@@@ in the command list, treats the rest of the parameter as a file and reads the parameters from that file. Examples of this functionality include the Standard LLLLiiiinnnnkkkkeeeerrrr and LLLLiiiibbbbrrrraaaarrrriiiiaaaannnn. The filename defined by EEEEXXXXTTTTEEEENNNNDDDDEEEEDDDD____LLLLIIIINNNNEEEE contains a list of command (including the .exe or .com extension) separated by a newlines. If the command is in upper case, the file name on the command line is set up with backslashes as the directory separator. Otherwise, slashes (Unix style) are used. This functionality allows the user to get round the 127 byte command line length limit of MSDOS. HHHHIIIISSSSTTTTFFFFIIIILLLLEEEE The file where command history is saved across login sessions. The default value is $$$$HHHHOOOOMMMMEEEE////hhhhiiiissssttttoooorrrryyyy....sssshhhh. HHHHOOOOMMMMEEEE The default argument (home directory) for the _c_d command. IIIIFFFFSSSS Internal field separators, normally ssssppppaaaacccceeee, ttttaaaabbbb, and nnnneeeewwww----lllliiiinnnneeee. MMMMAAAAIIIILLLL If this parameter is set to the name of a mail file _a_n_d the MMMMAAAAIIIILLLLPPPPAAAATTTTHHHH parameter is not set, the shell informs the user of the arrival of mail in the specified file. MMMMAAAAIIIILLLLCCCCHHHHEEEECCCCKKKK This parameter specifies how often (in seconds) the shell will check for the arrival of mail in the files specified by the MMMMAAAAIIIILLLLPPPPAAAATTTTHHHH or MMMMAAAAIIIILLLL parameters. If set to 0, the shell will check before each prompt. MMMMAAAAIIIILLLLPPPPAAAATTTTHHHH A semi-colon (;;;;) separated list of file names. If this parameter is set, the shell informs the user of the arrival of mail in any of the specified files. Each file name can be followed by %%%% and a message that will be printed when the modification time changes. The default message is "_y_o_u _h_a_v_e _m_a_i_l". PPPPAAAATTTTHHHH The search path for commands (see _E_x_e_c_u_t_i_o_n Page 5 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) below). The user may not change PPPPAAAATTTTHHHH if executing under _r_s_h. (Note that because a colon is used by MSDOS to indicate a drive, a semi-colon is used to separate the path names instead of a colon - this implies that the PATH variable must be set using single or double quotes to surround the value). The Shell automatically converts Unix format PPPPAAAATTTTHHHH assignments to MSDOS format when appropriate. A assignment is converted if there are no semi- colons, no backslashes and one or more colons. If there is only one colon, it must not be the second character of the new value. PPPPSSSS1111 Primary prompt string, by default ``$$$$ ''. PPPPSSSS2222 Secondary prompt string, by default ``>>>> ''. SSSSHHHHEEEELLLLLLLL When the shell is invoked, it scans the environment (see _E_n_v_i_r_o_n_m_e_n_t below) for this name. If it is found and there is an 'r' in the file name part of its value, the shell becomes a restricted shell. The shell also uses this variable to decide which program to spawn to interpret shell scripts (see _E_x_e_c_u_t_i_o_n below). TTTTMMMMPPPP The location of temporary files created by the shell. If this variable is not defined, the Shell uses the HHHHOOOOMMMMEEEE directory for temporary files. Failing that, the root directory of the current drive is used. The shell gives default values to PPPPAAAATTTTHHHH, PPPPSSSS1111, PPPPSSSS2222, SSSSHHHHEEEELLLLLLLL, HHHHOOOOMMMMEEEE and IIIIFFFFSSSS. BBBBllllaaaannnnkkkk IIIInnnntttteeeerrrrpppprrrreeeettttaaaattttiiiioooonnnn After parameter and command substitution, the results of substitution are scanned for internal field separator characters (those found in IIIIFFFFSSSS) and split into distinct arguments where such characters are found. Explicit null arguments ("""""""" or '''''''') are retained. Implicit null arguments (those resulting from _p_a_r_a_m_e_t_e_r_s that have no values) are removed. FFFFiiiilllleeee NNNNaaaammmmeeee GGGGeeeennnneeeerrrraaaattttiiiioooonnnn Following substitution, each command _w_o_r_d is scanned for the characters ****, ???? and [[[[. If one of these characters appears the word is regarded as a _p_a_t_t_e_r_n. The word is replaced with alphabetically sorted file names that match the pattern. If no file name is found that matches the pattern, the word is left unchanged. The character .... at the start of a file name or immediately following a ////, as well as the character //// itself, must be matched explicitly. When matching patterns for file names, the shell ignores the case of the pattern and the file directory entries. Generated file names are always in lower case. **** Matches any string, including the null string. Page 6 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) ???? Matches any single character. [[[[ ............ ]]]] Matches any one of the enclosed characters. A pair of characters separated by ---- matches any character lexically between the pair, inclusive. If the first character following the opening ``['' is a ````````!!!!'''''''' any character not enclosed is matched. If the shell has to open or create the file ////ddddeeeevvvv////ttttttttyyyy or ////ddddeeeevvvv////nnnnuuuullllllll (which are Unix special files), they are converted to the equivalent MSDOS file names (////ddddeeeevvvv////ccccoooonnnn and ////ddddeeeevvvv////nnnnuuuullll respectively). Any user programs which could expect ////ddddeeeevvvv////ttttttttyyyy or ////ddddeeeevvvv////nnnnuuuullllllll as arguments must do its own mapping to the MSDOS equivalents. QQQQuuuuoooottttiiiinnnngggg The following characters have a special meaning to the shell and cause termination of a word unless quoted: ;;;; &&&& (((( )))) |||| ^^^^ <<<< >>>> nnnneeeewwww----lllliiiinnnneeee ssssppppaaaacccceeee ttttaaaabbbb A character may be _q_u_o_t_e_d (i.e., made to stand for itself) by preceding it with a \\\\. The pair \\\\nnnneeeewwww----lllliiiinnnneeee is ignored. All characters enclosed between a pair of single quote marks (''''''''), except a single quote, are quoted. Inside double quote marks (""""""""), parameter and command substitution occurs and \\\\ quotes the characters \\\\, ````, """", and $$$$. """"$$$$****"""" is equivalent to """"$$$$1111 $$$$2222 ............"""", whereas """"$$$$@@@@"""" is equivalent to """"$$$$1111"""" """"$$$$2222"""" ............. PPPPrrrroooommmmppppttttiiiinnnngggg When used interactively, the shell prompts with the value of PPPPSSSS1111 before reading a command. If at any time a new-line is typed and further input is needed to complete a command, the secondary prompt (i.e., the value of PPPPSSSS2222) is issued. Many people like to have the shell provide them with useful information in their prompt. To accommodate this, the shell recognises special sequences of characters in the values of PPPPSSSS1111 and PPPPSSSS2222, and substitutes the appropriate information for them. The special sequences and what they signify are: %%%%dddd Place the current date, in the form DAY DD-MM-YY into the prompt. %%%%eeee Place the current event number (as defined by the hhhhiiiissssttttoooorrrryyyy command) into the prompt. If history evaluation has been turned off (via hhhhiiiissssttttoooorrrryyyy ----dddd), no number will be substituted in (i.e. the %%%%eeee will be removed). %%%%nnnn Place the current working drive into the prompt. Page 7 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) %%%%pppp Place the current working directory into the prompt. %%%%tttt Place the current time of day, in the form HH:MM into the prompt. The time is on a 24 hour clock, i.e. 1:30 in the afternoon will be 13:30. %%%%vvvv Place the MSDOS version number, in the form MSDOS MM:MM into the prompt. %%%%%%%% Place the character % into the prompt. \\\\xxxxxxxxxxxx Place the character _\_x_x_x into the prompt. The processing of escape sequences is the same as that for eeeecccchhhhoooo. Some of these facilities are of more use than others. IIIInnnnppppuuuutttt////OOOOuuuuttttppppuuuutttt Before a command is executed, its input and output may be redirected using a special notation interpreted by the shell. The following may appear anywhere in a simple- command or may precede or follow a _c_o_m_m_a_n_d and are _n_o_t passed on to the invoked command; substitution occurs before _w_o_r_d or _d_i_g_i_t is used: <<<<wwwwoooorrrrdddd Use file _w_o_r_d as standard input (file descriptor 0). >>>>wwwwoooorrrrdddd Use file _w_o_r_d as standard output (file descriptor 1). If the file does not exist it is created; otherwise, it is truncated to zero length. >>>>>>>>wwwwoooorrrrdddd Use file _w_o_r_d as standard output. If the file exists output is appended to it (by first seeking to the end-of-file); otherwise, the file is created. <<<<<<<<[----]wwwwoooorrrrdddd The shell input is read up to a line that is the same as _w_o_r_d, or to an end-of-file. The resulting document becomes the standard input. If any character of _w_o_r_d is quoted, no interpretation is placed upon the characters of the document; otherwise, parameter and command substitution occurs, (unescaped) \\\\nnnneeeewwww----lllliiiinnnneeee is ignored, and \\\\ must be used to quote the characters \\\\, $$$$, ````, and the first character of _w_o_r_d. If ---- is appended to <<<<<<<<, all leading tabs are stripped from _w_o_r_d and from the document. <<<<&&&&ddddiiiiggggiiiitttt Use the file associated with file descriptor _d_i_g_i_t as standard input. Similarly for the standard output using >>>>&&&&ddddiiiiggggiiiitttt. <<<<&&&&---- The standard input is closed. Similarly for Page 8 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) the standard output using >>>>&&&&----. nnnn<<<<>>>>wwwwoooorrrrdddd causes the file _w_o_r_d to be opened on file descriptor _n for both reading and writing. The file must already exist. If any of the above is preceded by a digit, the file descriptor which will be associated with the file is that specified by the digit (instead of the default 0 or 1). For example: ... 2>&1 associates file descriptor 2 with the file currently associated with file descriptor 1. The order in which redirections are specified is significant. The shell evaluates redirections left-to- right. For example: ... 1>_x_x_x 2>&1 first associates file descriptor 1 with file _x_x_x. It associates file descriptor 2 with the file associated with file descriptor 1 (i.e. _x_x_x). If the order of redirections were reversed, file descriptor 2 would be associated with the terminal (assuming file descriptor 1 had been) and file descriptor 1 would be associated with file _x_x_x . The environment for the execution of a command contains the file descriptors of the invoking shell as modified by input/output specifications. Redirection of output is not allowed in the restricted shell. EEEEnnnnvvvviiiirrrroooonnnnmmmmeeeennnntttt The _e_n_v_i_r_o_n_m_e_n_t (see _e_n_v_i_r_o_n(5)) is a list of name-value pairs that is passed to an executed program in the same way as a normal argument list. The shell interacts with the environment in several ways. On invocation, the shell scans the environment and creates a parameter for each name found, giving it the corresponding value. If the user modifies the value of any of these parameters or creates new parameters, none of these affects the environment unless the eeeexxxxppppoooorrrrtttt command is used to bind the shell's parameter to the environment (see also sssseeeetttt ----aaaa). A parameter may be removed from the environment with the uuuunnnnsssseeeetttt command. The environment seen by any executed command is thus composed of any unmodified name-value pairs originally inherited by the shell, minus any pairs removed by uuuunnnnsssseeeetttt, plus any modifications or additions, all of which must be noted in eeeexxxxppppoooorrrrtttt commands. Page 9 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) The environment for any _s_i_m_p_l_e-_c_o_m_m_a_n_d may be augmented by prefixing it with one or more assignments to parameters. Thus: TERM=450 cmd args and (export TERM; TERM=450; cmd args) are equivalent (as far as the execution of _c_m_d is concerned). If the ----kkkk flag is set, _a_l_l keyword arguments are placed in the environment, even if they occur after the command name. The following first prints aaaa====bbbb cccc and cccc: echo a=b c set -k echo a=b c SSSSiiiiggggnnnnaaaallllssss The INTERRUPT and QUIT signals for an invoked command are ignored if the command is followed by &&&&; otherwise signals have the values inherited by the shell from its parent, with the exception of signal 11 (but see also the ttttrrrraaaapppp command below). HHHHiiiissssttttoooorrrryyyy When reading input from an interactive terminal, a ``!'' at the start of a line signals to the shell that it should attempt to perform a history subsitution. A history subsitution is a short-hand method which allows the user to recall a previous command for execution or editing. The recalled command is placed in the command line for editing or passing to the rest of the shell for normal processing. A history substitution takes the form: !!!! [ ! | _s_t_r | _n_u_m ] _t_e_r_m_i_n_a_t_o_r !!!!!!!! will place the previous command in the command line. !!!!_n_u_m will place the history command with the specified number in the command line. !!!!_s_t_r will find the most recent command line that started with the characters in _s_t_r. The _t_e_r_m_i_n_a_t_o_r determines what action is performed after the history line has been found. If the original history command is entered using the <<<<rrrreeeettttuuuurrrrnnnn>>>> key, the new command line is passed directly to the shell. If the <<<<eeeennnndddd>>>> key is pressed, the new command line can be edited in the manner described below. CCCCoooommmmmmmmaaaannnndddd LLLLiiiinnnneeee EEEEddddiiiittttiiiinnnngggg When reading input from an interactive terminal, certain keystrokes allow the current input line to be edited. The Page 10 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) following keystrokes corresponding to the following functions are defined in the initialisation file sssshhhh....iiiinnnniiii. The keywords in the initialisation file which provide the functions are listed below: RRRRiiiigggghhhhtttt Move the cursor right one character WWWWoooorrrrddddRRRRiiiigggghhhhtttt Move the cursor right one word LLLLeeeefffftttt Move the cursor left one character WWWWoooorrrrddddLLLLeeeefffftttt Move the cursor left one word PPPPrrrreeeevvvviiiioooouuuussss Get the previous command from the history file NNNNeeeexxxxtttt Get the next command from the history file IIIInnnnsssseeeerrrrtttt Toggle insert/overwrite mode (note the shape of the cursor changes to indicate the current mode) DDDDeeeelllleeeetttteeeeRRRRiiiigggghhhhtttt Delete the current character unless the cursor is at the end of line when no action is taken SSSSttttaaaarrrrtttt Move the cursor to the start of the command CCCCoooommmmpppplllleeeetttteeee Attempt to complete the filename. The shell attempts to complete the file name at the current cursor position. The file name is delimited by white space characters. If the shell is unable to complete the file name (ie no match can be found in the appropriate directory), the bell is rung. If a single match is found, the new file name is displayed. If multiple matches are found, the file name is replaced by the longest non-unique part of the file name and the bell is rung. EEEEnnnndddd Move the cursor to the end of the command, unless the first character of the command is a !!!!, in which case the appropriate history search is done. The cursor is placed at the end of the command line. FFFFlllluuuusssshhhh Delete to the end of the line Page 11 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) SSSSccccaaaannnnBBBBaaaacccckkkkwwwwaaaarrrrdddd Search backwards from the current history command for the next match against the last history request or the string currently in the command line if there has been no previous history request. SSSSccccaaaannnnFFFFoooorrrreeeewwwwaaaarrrrdddd Search forewards from the current history command for the next match against the last history request or the string currently in the command line if there has been no previous history request. CCCClllleeeeaaaarrrr Erase the complete line. DDDDiiiirrrreeeeccccttttoooorrrryyyy Display the file name list matching the partially entered file name under the cursor. If no matches are found the bell is rung. To display the whole directory, enter the directory name followed by a slash ////. After the directory listing has been displayed, the entered command line is redisplayed. DDDDeeeelllleeeetttteeeeLLLLeeeefffftttt Delete the character to the left of the cursor. RRRReeeettttuuuurrrrnnnn Execute the command line, unless the first character of the command is a !!!!, in which case the appropriate history processing is done. _T_h_i_s _i_s _t_h_e _a_c_t_u_a_l _k_e_y _p_r_e_s_s_e_d _a_n_d _c_a_n_n_o_t _b_e _m_o_d_i_f_i_e_d _b_y _t_h_e _i_n_i_t_i_a_l_i_s_a_t_i_o_n _f_i_l_e. IIIInnnniiiittttiiiiaaaalllliiiissssaaaattttiiiioooonnnn FFFFiiiilllleeee When the shell is run in interactive mode, the Command Line Editing keys and other user configuration parameters are read from the initialisation file _s_h._i_n_i. This shell looks for this file in the same directory as the sssshhhh executable which is running. It does not use the SSSSHHHHEEEELLLLLLLL environment variable or search the directories in the PPPPAAAATTTTHHHH environment variable. At present, there are two types of entry in this file: keyboard configuration; and others. The entry is contained in a single line and consists of a keyword (in upper or lower case), white space, an equals symbols, white space and one or two numeric values (see _s_t_r_t_o_l for valid formats where _b_a_s_e parameter is zero), followed by an end of line character. For the keyboard entries, the numeric values give the MSDOS Function 8 (Console Input without Echo) return values for that entry. Note that extended codes (function keys) require two calls to this function. The first call returns Page 12 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) zero and the second the extended code. In the configuration file, a first numeric value of zero indicates a extended code and must be followed by a second value. A non-zero first numeric value must not be followed by anything else on the line. Other entries must only have one numeric value. A zero value disables the function and a non-zero value enables the function. At present, there are two other functions: BBBBeeeellllllll Enable/disable warning bells HHHHaaaallllffffHHHHeeeeiiiigggghhhhtttt Use full or halfheight block cursor to indicate Insert mode Invalid lines or lines beginning with a #### are ignored. The following table gives the list of valid keywords and their default values: _________________________________________________________________________ Keyword First numeric Second numeric Actual Key _________________________________________________________________________ KEYBOARD ENTRIES ScanBackward 0 0x49 PAGE UP ScanForeward 0 0x51 PAGE DOWN Previous 0 0x48 UP ARROW Next 0 0x50 DOWN ARROW Left 0 0x4b LEFT ARROW Right 0 0x4d RIGHT ARROW WordRight 0 0x74 Control RIGHT ARROW WordLeft 0 0x73 Control LEFT ARROW Start 0 0x47 HOME Clear 0 0x76 Control PAGE DOWN Flush 0 0x75 Control END End 0 0x4f END Insert 0 0x52 INSERT DeleteRight 0 0x53 DELETE DeleteLeft 0x08 BACKSPACE Complete 0 0x77 Control HOME Directory 0 0x0f Shift TAB _________________________________________________________________________ OTHER FUNCTIONS Bell 0 HalfHeight 0 _________________________________________________________________________ EEEExxxxeeeeccccuuuuttttiiiioooonnnn Each time a command is executed, the above substitutions are carried out. If the command name matches one of the _S_p_e_c_i_a_l _C_o_m_m_a_n_d_s listed below, it is executed in the shell process. If the command name does not match a _S_p_e_c_i_a_l _C_o_m_m_a_n_d, but matches the name of a defined function, the function is executed in the shell process (note how this differs from Page 13 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) the execution of shell procedures). The positional parameters $$$$1111, $$$$2222, .... are set to the arguments of the function. If the command name matches neither a _S_p_e_c_i_a_l _C_o_m_m_a_n_d nor the name of a defined function, a new process is created and an attempt is made to execute the command via _e_x_e_c(2). The shell parameter PPPPAAAATTTTHHHH defines the search path for the directory containing the command. Alternative directory names are separated by a semi-colon (;;;;). The default path is ;;;;cccc::::////bbbbiiiinnnn;;;;cccc::::////uuuussssrrrr////bbbbiiiinnnn (specifying the current directory, cccc::::////bbbbiiiinnnn, and cccc::::////uuuussssrrrr////bbbbiiiinnnn, in that order). Note that the current directory is specified by a null path name, which can appear immediately after the equal sign or between the semi-colon delimiters anywhere else in the path list. If the command name contains a //// or starts with xxxx:::: (where x is a drive letter) the search path is not used; such commands will not be executed by the restricted shell. Otherwise, each directory in the path is searched for an executable file. Executable files are indicated by a .exe or .com extension. This extension is automatically supplied by the shell and not have to be entered by the user. If the file with a .com or .exe extension cannot be found in the directory, the file is opened and first 512 characters are read. If there are no characters in the block with a value in the range 0 to 7, the file is assumed to be a script file containing shell commands. Note that the shell will check the file and if that file does not exist or is not a script, it will try the file with an extension of ....sssshhhh. If a ....sssshhhh file is found, that will be processed. A sub-shell (given by the environment variable SSSSHHHHEEEELLLLLLLL) is spawned to read it. If the script file starts with the a line of the form #! _i_n_t_e_r_p_r_e_t_e_r [_a_r_g_u_m_e_n_t_s], the interpreter is invoked instead of the shell to process the script. Optional arguments can be supplied in the script file which are passed before the name of the script file. Thus, if the file _d_e_m_o contained the following string as the first line #! perl -sP Entering _d_e_m_o _n_a_m_e would be equivalent to entering the _p_e_r_l -_s_P _n_a_m_e at the command prompt. Note that no other processing of the first line other that the separation (by white space) into arguments is done. If none of the above conditions for a executable file are detected and a file with a .bat extension exists in the directory, the command processor given by the CCCCOOOOMMMMSSSSPPPPEEEECCCC environment variable is spawned to process the file. This Page 14 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) is normally the standard MSDOS _c_o_m_m_a_n_d._c_o_m processor. A parenthesized command is also executed in a sub-shell. SSSSppppeeeecccciiiiaaaallll CCCCoooommmmmmmmaaaannnnddddssss Input/output redirection is permitted for these commands. File descriptor 1 is the default output location. :::: No effect; the command does nothing. A zero exit code is returned. _l_e_t_t_e_r:::: Select the drive specified by _l_e_t_t_e_r. .... _f_i_l_e Read and execute commands from _f_i_l_e and return. The search path specified by PPPPAAAATTTTHHHH is used to find the directory containing _f_i_l_e. bbbbrrrreeeeaaaakkkk [ _n ] Exit from the enclosing ffffoooorrrr or wwwwhhhhiiiilllleeee loop, if any. If _n is specified, break _n levels. bbbbuuuuiiiillllttttiiiinnnn [ _a_r_g_s ... ] Force the selection of the bbbbuuuuiiiillllttttiiiinnnn version of a command. The builtin shell command selected by the first _a_r_g_s value is executed with the parameters defined by the remaining _a_r_g_ss. If no arguments are given, a list of all _b_u_i_l_t_i_n commands is printed. If the first argument is one of the following, the processing of the builtin command in the following arguments are changed as indicated: ----aaaa Set the following builtin commands to use builtin version in preference to any function or external versions. ----dddd Set the following builtin commands to use the function or external version in preference to the builtin version. ----ssss Display the current status of the following builtin commands. ccccoooonnnnttttiiiinnnnuuuueeee [ _n ] Resume the next iteration of the enclosing ffffoooorrrr or wwwwhhhhiiiilllleeee loop. If _n is specified, resume at the _n-th enclosing loop. ccccdddd [ _a_r_g ] Change the current directory to _a_r_g. The shell parameter HHHHOOOOMMMMEEEE is the default _a_r_g. The shell parameter CCCCDDDDPPPPAAAATTTTHHHH defines the search path for the directory containing _a_r_g. Alternative directory names are separated by a semi-colon (;;;;). The default path is <<<<nnnnuuuullllllll>>>> (specifying the current directory). Note that the current directory is specified by a null path name, which can appear immediately after the equal sign or between the semi-colon delimiters anywhere else in the path list. If _a_r_g begins with a //// or xxxx:::: (where x is a Page 15 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) drive letter), the search path is not used. Otherwise, each directory in the path is searched for _a_r_g. The _c_d command may not be executed by _r_s_h. eeeecccchhhhoooo [ _a_r_g ... ] Echo arguments. EEEEcccchhhhoooo writes its arguments separated by blanks and terminated by a new-line on the standard output. It also understands C-like escape conventions; beware of conflicts with the shell's use of \\\\: \\\\bbbb backspace \\\\cccc print line without new-line \\\\ffff form-feed \\\\nnnn new-line \\\\rrrr carriage return \\\\tttt tab \\\\vvvv vertical tab \\\\\\\\ backslash \\\\_n the 8-bit character whose ASCII code is the 1-, 2- or 3-digit octal number _n, which must start with a zero. _E_c_h_o is useful for producing diagnostics in command files and for sending known data into a pipe. eeeevvvvaaaallll [ _a_r_g ... ] The arguments are read as input to the shell and the resulting command(s) executed. eeeexxxxeeeecccc [ _a_r_g ... ] The command specified by the arguments is executed in place of this shell without creating a new process. Input/output arguments may appear and, if no other arguments are given, cause the shell input/output to be modified. eeeexxxxiiiitttt [ _n ] Causes a shell to exit with the exit status specified by _n. If _n is omitted the exit status is that of the last command executed (an end-of-file will also cause the shell to exit.) eeeexxxxppppoooorrrrtttt [ _n_a_m_e ... ] The given _n_a_m_es are marked for automatic export to the _e_n_v_i_r_o_n_m_e_n_t of subsequently-executed commands. If no arguments are given, a list of all names that are exported in this shell is printed. Function names may _n_o_t be exported. ggggeeeettttoooopppptttt _o_p_t_s_t_r_i_n_g _n_a_m_e [ _a_r_g_s ... ] Parse command options and write them to standard output. GGGGeeeettttoooopppptttt is used to break up options in command lines for easy parsing by shell procedures and to check for legal options. _O_p_t_s_t_r_i_n_g is a string of recognized Page 16 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) option letters (see _g_e_t_o_p_t(3C)); if a letter is followed by a colon, the option is expected to have an argument which may or may not be separated from it by white space. The special option -------- is used to delimit the end of the options. If it is used explicitly, ggggeeeettttoooopppptttt will recognize it; otherwise, ggggeeeettttoooopppptttt will generate it; in either case, ggggeeeettttoooopppptttt will place it at the end of the options. Each option is preceded by a ---- and is in its own positional parameter; each option argument is also parsed into its own positional parameter. The following code fragment shows how one might process the arguments for a command that can take the options aaaa or bbbb, as well as the option oooo, which requires an argument: set -- `getopt abo: $*` if [ $? != 0 ] then echo $USAGE exit 2 fi for i in $* do case $i in -a | -b) FLAG=$i; shift;; -o) OARG=$2; shift 2;; --) shift; break;; esac done This code will accept any of the following as equivalent: cmd -aoarg file file cmd -a -o arg file file cmd -oarg -a file file cmd -a -oarg -- file file hhhhiiiissssttttoooorrrryyyy [ ----ddddeeeeiiii ] The hhhhiiiissssttttoooorrrryyyy command, with no arguments, will print all the commands that are currently saved in the shell's history buffers. As new commands are executed, and space in the buffers runs out, old commands will be deleted. The hhhhiiiissssttttoooorrrryyyy commands prints out the stored commands with sequence numbers. Negative numbered commands, through command number zero, are commands that were retrieved from the saved history file. Commands starting at one were entered during the current login session. If a saved command contains embedded newlines, these will be printed out as the Page 17 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) sequence \\\\nnnn, so that individual command stay on one line. The arguments changes the way the shell processes history information as follows: ----dddd Disable the saving of commands in the history file. ----eeee Enable the saving of commands in the history file. ----iiii Initialise the history file. mmmmssssddddoooossss [ _n_a_m_e ... ] The given _n_a_m_es are marked _m_s_d_o_s format and if the ----mmmm flag is set, the values of the these _n_a_m_es are exported to child processes with any slashes in the value replaced by backslashes. If no arguments are given, a list of all _m_s_d_o_s names is printed. ppppwwwwdddd Print the current working directory. rrrreeeeaaaadddd [ _n_a_m_e ... ] One line is read from the standard input and the first word is assigned to the first _n_a_m_e, the second word to the second _n_a_m_e, etc., with leftover words assigned to the last _n_a_m_e. The return code is 0 unless an end-of- file is encountered. rrrreeeeaaaaddddoooonnnnllllyyyy [ _n_a_m_e ... ] The given _n_a_m_es are marked _r_e_a_d_o_n_l_y and the values of the these _n_a_m_es may not be changed by subsequent assignment. If no arguments are given, a list of all _r_e_a_d_o_n_l_y names is printed. rrrreeeettttuuuurrrrnnnn [ _n ] Causes a function to exit with the return value specified by _n. If _n is omitted, the return status is that of the last command executed. sssseeeetttt [ --------aaaaeeeeffffkkkkmmmmnnnnttttuuuuvvvvxxxx [ _a_r_g ... ] ] ----aaaa Mark variables which are modified or created for export. ----eeee Exit immediately if a command exits with a non- zero exit status. ----ffff Disable file name generation ----kkkk All keyword arguments are placed in the environment for a command, not just those that Page 18 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) precede the command name. ----mmmm For those variables marked as mmmmssssddddoooossss variables, the values are exported to child processes with the slashes replaced by backslashes. Most MSDOS utilities do not care if a file name contains a slash or backslash as a directory separator. However, some like the _l_i_n_k_e_r require backslashes in the value of the LLLLIIIIBBBB variable. ----nnnn Read commands but do not execute them. ----tttt Exit after reading and executing one command. ----uuuu Treat unset variables as an error when substituting. ----vvvv Print shell input lines as they are read. ----xxxx Print commands and their arguments as they are executed. -------- Do not change any of the flags; useful in setting $$$$1111 to ----. Using ++++ rather than ---- causes these flags to be turned off. These flags can also be used upon invocation of the shell. The current set of flags may be found in $$$$----. The remaining arguments are positional parameters and are assigned, in order, to $$$$1111, $$$$2222, .... If no arguments are given the values of all names are printed. sssshhhhiiiifffftttt [ _n ] The positional parameters from $$$$nnnn++++1111 ... are renamed $$$$1111 .... If _n is not given, it is assumed to be 1. sssswwwwaaaapppp [ _o_p_t_i_o_n_s ] This command defines how the shell will handle swapping. The options are ooooffffffff Disable swapping. The shell remains in memory whilst the child is running and reduces the available memory by about 200K (depending on the size of the environment and history). oooonnnn Enable all devices. The shell will swap out to either expanded or extended memory or to disk, execute the command and then swap back in. Whilest swapped, the shell reduces the available memory by about 3K. Page 19 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) eeeexxxxppppaaaannnndddd Enable swapping to Expanded Memory. The EMS driver must exist on your system for this to work. eeeexxxxtttteeeennnntttt [ _s_t_a_r_t _a_d_d_r_e_s_s ] Enable swapping to Extended Memory. If you have an XMS driver on your system, the shell will use the XMS driver. Otherwise, the BIOS Interrupt 15 interface is used. The optional start address defines the based address in the Extended Memory at which point the shell writes its swap area when the BIOS interface is used. The default location is _0_x_1_0_0_0_0_0. ddddiiiisssskkkk Enable swapping to disk. The shell creates a temporary file and saves itself in it. On completion, the file is deleted. This is the slowest method of swapping. With no options, the current swapping options are displayed. tttteeeesssstttt _e_x_p_r or [[[[ _e_x_p_r ]]]] Evaluate conditional expressions. TTTTeeeesssstttt evaluates the expression _e_x_p_r and, if its value is true, returns a zero (true) exit status; otherwise, a non-zero (false) exit status is returned; tttteeeesssstttt also returns a non-zero exit status if there are no arguments. The following primitives are used to construct eeeexxxxpppprrrr: ----rrrr _f_i_l_e true if _f_i_l_e exists and is readable. ----wwww _f_i_l_e true if _f_i_l_e exists and is writable. ----xxxx _f_i_l_e true if _f_i_l_e exists and is executable. ----ffff _f_i_l_e true if _f_i_l_e exists and is a regular file. ----dddd _f_i_l_e true if _f_i_l_e exists and is a directory. ----cccc _f_i_l_e true if _f_i_l_e exists and is a character special file. ----bbbb _f_i_l_e true if _f_i_l_e exists and is a block special file. ----ssss _f_i_l_e true if _f_i_l_e exists and has a size greater than zero. ----tttt [ _f_i_l_d_e_s ] true if the open file whose file descriptor number is _f_i_l_d_e_s (1 by default) is Page 20 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) associated with a terminal device. ----zzzz _s_1 true if the length of the string _s_1 is zero. ----nnnn _s_1 true if the length of the string _s_1 is non-zero. _s_1 ==== _s_2 true if strings _s_1 and _s_2 are identical. _s_1 !!!!==== _s_2 true if strings _s_1 and _s_2 are _n_o_t identical. _s_1 true if _s_1 is _n_o_t the null string. _n_1 ----eeeeqqqq _n_2 true if the integers _n_1 and _n_2 are algebraically equal. Any of the comparisons ----nnnneeee, ----ggggtttt, ----ggggeeee, ----lllltttt, and ----lllleeee may be used in place of RRRR----eeeeqqqq. These primaries may be combined with the following operators: !!!! unary negation operator. ----aaaa binary _a_n_d operator. ----oooo binary _o_r operator (----aaaa has higher precedence than ----oooo). (((( expr )))) parentheses for grouping. Notice that all the operators and flags are separate arguments to tttteeeesssstttt. Notice also that parentheses are meaningful to the shell and, therefore, must be escaped. ttttrrrraaaapppp [ _a_r_g ] [ _n ] ... The command _a_r_g is to be read and executed when the shell receives signal(s) _n. (Note that _a_r_g is scanned once when the trap is set and once when the trap is taken.) Trap commands are executed in order of signal number. Any attempt to set a trap on a signal that was ignored on entry to the current shell is ineffective. An attempt to trap on signal 11 (memory fault) produces an error. If _a_r_g is absent all trap(s) _n are reset to their original values. If _a_r_g is the null string this signal is ignored by the shell and by the commands it invokes. If _n is 0 the command _a_r_g is executed on exit from the shell. The ttttrrrraaaapppp command with no arguments prints a list of commands associated with each signal number. Page 21 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) ttttyyyyppppeeee [ _n_a_m_e ... ] For each _n_a_m_e, indicate how it would be interpreted if used as a command name. uuuummmmaaaasssskkkk [ _n_n_n ] The user file-creation mask is set to _n_n_n (see _u_m_a_s_k(2)). If _n_n_n is omitted, the current value of the mask is printed. uuuunnnnsssseeeetttt [ _n_a_m_e ... ] For each _n_a_m_e, remove the corresponding variable or function. The variables PPPPAAAATTTTHHHH, PPPPSSSS1111, PPPPSSSS2222, and IIIIFFFFSSSS cannot be unset. vvvveeeerrrr Display the current version of the shell. IIIInnnnvvvvooooccccaaaattttiiiioooonnnn If the shell is invoked through _e_x_e_c(2) and the first character of argument zero is ---- or the ----0000(zero) switch is in the invokation line, commands are initially read from ////eeeettttcccc////pppprrrrooooffffiiiilllleeee....sssshhhh and from $$$$HHHHOOOOMMMMEEEE////pppprrrrooooffffiiiilllleeee....sssshhhh, if such files exist. Thereafter, commands are read as described below, which is also the case when the shell is invoked as ////bbbbiiiinnnn////sssshhhh. The flags below are interpreted by the shell on invocation only; Note that unless the ----cccc or ----ssss flag is specified, the first argument is assumed to be the name of a file containing commands, and the remaining arguments are passed as positional parameters to that command file: ----cccc string If the ----cccc flag is present commands are read from _s_t_r_i_n_g. ----ssss If the ----ssss flag is present or if no arguments remain commands are read from the standard input. Any remaining arguments specify the positional parameters. Shell output (except for _S_p_e_c_i_a_l _C_o_m_m_a_n_d_s) is written to file descriptor 2. ----iiii If the ----iiii flag is present or if the shell input and output are attached to a terminal, this shell is _i_n_t_e_r_a_c_t_i_v_e. In this case, the TERMINATE signal is ignored and the INTERRUPT signal is caught and ignored. In all cases, the QUIT signal is ignored by the shell. ----rrrr If the ----rrrr flag is present, the shell is a restricted shell. ----0000(zero) If the ----0000(zero) flag is present, this has the same effect as starting the shell with the first character of argument zero as a ---- (see above). The remaining flags and arguments are described under the sssseeeetttt command above. RRRRsssshhhh OOOOnnnnllllyyyy PPPPaaaaggggeeee 22222222 ((((pppprrrriiiinnnntttteeeedddd 11111111////6666////99990000)))) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) _R_s_h is used to set up login names and execution environments whose capabilities are more controlled than those of the standard shell. The actions of _r_s_h are identical to those of _s_h, except that the following are disallowed: changing directory (see _c_d(1)), setting the value of $$$$PPPPAAAATTTTHHHH specifying path or command names containing ////, redirecting output (>>>> and >>>>>>>>). The restrictions above are enforced after pppprrrrooooffffiiiilllleeee....sssshhhh is interpreted. When a command to be executed is found to be a shell procedure, _r_s_h invokes _s_h to execute it. Thus, it is possible to provide to the end-user shell procedures that have access to the full power of the standard shell, while imposing a limited menu of commands; this scheme assumes that the end-user does not have write and execute permissions in the same directory. The net effect of these rules is that the writer of the pppprrrrooooffffiiiilllleeee....sssshhhh has complete control over user actions, by performing guaranteed setup actions and leaving the user in an appropriate directory (probably _n_o_t the login directory). The system administrator often sets up a directory of commands (i.e., ////uuuussssrrrr////rrrrbbbbiiiinnnn) that can be safely invoked by _r_s_h. Some systems also provide a restricted editor _r_e_d. EEEEXXXXIIIITTTT SSSSTTTTAAAATTTTUUUUSSSS Errors detected by the shell, such as syntax errors, cause the shell to return a non-zero exit status. If the shell is being used non-interactively execution of the shell file is abandoned. Otherwise, the shell returns the exit status of the last command executed (see also the eeeexxxxiiiitttt command above). FFFFIIIILLLLEEEESSSS /etc/profile.sh $HOME/profile.sh $TMP/sh* ??/sh.ini CCCCRRRRIIIITTTTIIIICCCCAAAALLLL EEEERRRRRRRROOOORRRRSSSS The Shell provide a Critical Error Handler (Interrupt 24) similar to the standard MSDOS handler. In addition to the standard message, the handler also displays the Extended Error Code information in hexadecimal. LLLLIIIIMMMMIIIIIIIITTTTAAAATTTTIIIIOOOONNNNSSSS Any TSR (Terminate Stay Resident) programs must be loaded before loading _S_h as the shell will overwrite the TSR when it reloads itself after swapping out. Page 23 (printed 11/6/90) SSSSHHHH((((1111LLLL)))) MMMMSSSS----DDDDOOOOSSSS VVVVeeeerrrrssssiiiioooonnnn 1111....6666 ((((DDDDaaaattttaaaa LLLLooooggggiiiicccc LLLLiiiimmmmiiiitttteeeedddd)))) SSSSHHHH((((1111LLLL)))) SSSSEEEEEEEE AAAALLLLSSSSOOOO cd(1), env(1), test(1), umask(1). dup(2), exec(2), pipe(2), signal(2), umask(2), wait(2), strtol(3), profile(4), environ(5) in the _U_N_I_X _S_y_s_t_e_m _P_r_o_g_r_a_m_m_e_r _R_e_f_e_r_e_n_c_e _M_a_n_u_a_l. Page 24 (printed 11/6/90)