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Text File | 1995-07-26 | 11.4 KB | 265 lines

eeeexxxxeeeecccc((((nnnn)))) TTTTccccllll ((((7777....0000)))) eeeexxxxeeeecccc((((nnnn)))) _________________________________________________________________ NNNNAAAAMMMMEEEE exec - Invoke subprocess(es) SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS eeeexxxxeeeecccc ?_s_w_i_t_c_h_e_s? _a_r_g ?_a_r_g ...? _________________________________________________________________ DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN This command treats its arguments as the specification of one or more subprocesses to execute. The arguments take the form of a standard shell pipeline where each _a_r_g becomes one word of a command, and each distinct command becomes a subprocess. If the initial arguments to eeeexxxxeeeecccc start with ---- then they are | treated as command-line switches and are not part of the | pipeline specification. The following switches are | currently supported: | ----kkkkeeeeeeeeppppnnnneeeewwwwlllliiiinnnneeee || Retains a trailing newline in the pipeline's | output. Normally a trailing newline will be | deleted. | -------- || Marks the end of switches. The argument | following this one will be treated as the first | _a_r_g even if it starts with a ----.... If an _a_r_g (or pair of _a_r_g's) has one of the forms described below then it is used by eeeexxxxeeeecccc to control the flow of input and output among the subprocess(es). Such arguments will not be passed to the subprocess(es). In forms such as ``< | _f_i_l_e_N_a_m_e'' _f_i_l_e_N_a_m_e may either be in a separate argument | from ``<'' or in the same argument with no intervening space | (i.e. ``<_f_i_l_e_N_a_m_e''). | Separates distinct commands in the pipeline. The standard output of the preceding command will be piped into the standard input of the next command. |& Separates distinct commands in the pipeline. Both standard output and standard error of the preceding command will be piped into the standard input of the next command. This form of redirection overrides forms such as 2> and >&. Page 1 (printed 7/17/95) eeeexxxxeeeecccc((((nnnn)))) TTTTccccllll ((((7777....0000)))) eeeexxxxeeeecccc((((nnnn)))) < _f_i_l_e_N_a_m_e The file named by _f_i_l_e_N_a_m_e is opened and used as the standard input for the first command in the pipeline. <@ _f_i_l_e_I_d _F_i_l_e_I_d must be the identifier for an open | file, such as the return value from a | previous call to ooooppppeeeennnn. It is used as the | standard input for the first command in the | pipeline. _F_i_l_e_I_d must have been opened for | reading. << _v_a_l_u_e _V_a_l_u_e is passed to the first command as its standard input. > _f_i_l_e_N_a_m_e Standard output from the last command is redirected to the file named _f_i_l_e_N_a_m_e, overwriting its previous contents. 2> _f_i_l_e_N_a_m_e Standard error from all commands in the | pipeline is redirected to the file named | _f_i_l_e_N_a_m_e, overwriting its previous contents. | >& _f_i_l_e_N_a_m_e || Both standard output from the last command | and standard error from all commands are | redirected to the file named _f_i_l_e_N_a_m_e, | overwriting its previous contents. >> _f_i_l_e_N_a_m_e Standard output from the last command is redirected to the file named _f_i_l_e_N_a_m_e, appending to it rather than overwriting it. 2>> _f_i_l_e_N_a_m_e Standard error from all commands in the | pipeline is redirected to the file named | _f_i_l_e_N_a_m_e, appending to it rather than | overwriting it. | >>& _f_i_l_e_N_a_m_e || Both standard output from the last command | and standard error from all commands are | redirected to the file named _f_i_l_e_N_a_m_e, | appending to it rather than overwriting it. | >@ _f_i_l_e_I_d || _F_i_l_e_I_d must be the identifier for an open | file, such as the return value from a | previous call to ooooppppeeeennnn. Standard output from | the last command is redirected to _f_i_l_e_I_d's | file, which must have been opened for | writing. | 2>@ _f_i_l_e_I_d || Page 2 (printed 7/17/95) eeeexxxxeeeecccc((((nnnn)))) TTTTccccllll ((((7777....0000)))) eeeexxxxeeeecccc((((nnnn)))) _F_i_l_e_I_d must be the identifier for an open | file, such as the return value from a | previous call to ooooppppeeeennnn. Standard error from | all commands in the pipeline is redirected to | _f_i_l_e_I_d's file. The file must have been | opened for writing. | >&@ _f_i_l_e_I_d || _F_i_l_e_I_d must be the identifier for an open | file, such as the return value from a | previous call to ooooppppeeeennnn. Both standard output | from the last command and standard error from | all commands are redirected to _f_i_l_e_I_d's file. | The file must have been opened for writing. If standard output has not been redirected then the eeeexxxxeeeecccc command returns the standard output from the last command in the pipeline. If any of the commands in the pipeline exit abnormally or are killed or suspended, then eeeexxxxeeeecccc will return an error and the error message will include the pipeline's output followed by error messages describing the abnormal terminations; the eeeerrrrrrrroooorrrrCCCCooooddddeeee variable will contain additional information about the last abnormal termination encountered. If any of the commands writes to its standard error file and that standard error isn't redirected, then eeeexxxxeeeecccc will return an error; the error message will include the pipeline's standard output, followed by messages about abnormal terminations (if any), followed by the standard error output. If the last character of the result or error message is a newline then that character is normally deleted from the result or error message. This is consistent with other Tcl return values, which don't normally end with newlines. | However, if ----kkkkeeeeeeeeppppnnnneeeewwwwlllliiiinnnneeee is specified then the trailing | newline is retained. If standard input isn't redirected with ``<'' or ``<<'' or ``<@'' then the standard input for the first command in the pipeline is taken from the application's current standard input. If the last _a_r_g is ``&'' then the pipeline will be executed in background. In this case the eeeexxxxeeeecccc command will return a | list whose elements are the process identifiers for all of | the subprocesses in the pipeline. The standard output from the last command in the pipeline will go to the application's standard output if it hasn't been redirected, and error output from all of the commands in the pipeline will go to the application's standard error file unless redirected. Page 3 (printed 7/17/95) eeeexxxxeeeecccc((((nnnn)))) TTTTccccllll ((((7777....0000)))) eeeexxxxeeeecccc((((nnnn)))) The first word in each command is taken as the command name; tilde-substitution is performed on it, and if the result contains no slashes then the directories in the PATH environment variable are searched for an executable by the given name. If the name contains a slash then it must refer to an executable reachable from the current directory. No ``glob'' expansion or other shell-like substitutions are performed on the arguments to commands. KKKKEEEEYYYYWWWWOOOORRRRDDDDSSSS execute, pipeline, redirection, subprocess Page 4 (printed 7/17/95)