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GREP: A FILE SEARCH UTILITY --------------------------- TABLE OF CONTENTS ----------------- 1. What is GREP? 2. GREP Options 3. The Search String 4. Operators in Regular Expressions 5. The File Specification 6. GREP Examples 1. WHAT IS GREP? ---------------- GREP is a powerful search utility that can search for text in several files at once. The general command-line syntax for GREP follows: grep [options] searchstring filespec [filespec filespec ...filespec] For example, if you want to see in which source files you call the setupmodem function, you could use GREP to search the contents of all the .ASM files in your directory to look for the string setupmodem, like this: grep setupmodem *.asm 2. GREP OPTIONS --------------- In the command line, options are one or more single characters preceded by a hyphen symbol (-). Each individual character is a switch that you can turn on or off: type the plus (+) after a character to turn the option on, or type a hyphen (-) after the character to turn the option off. The default is on (the + is implied): for example, -r means the same thing as -r+. You can list multiple options individually (like this: -i -d -l), or you can combine them (like this: -ild or -il -d, and so forth); they're all the same to GREP. Here is a list of the option characters used with GREP and their meanings: -c Count only: Only a count of matching lines is printed. For each file that contains at least one matching line, GREP prints the file name and a count of the number of matching lines. Matching lines are not printed. -d Directories: For each filespec specified on the command line, GREP searches for all files that match the file specification, both in the directory specified and in all subdirectories below the specified directory. If you give a filespec without a path, GREP assumes the files are in the current directory. -i Ignore case: GREP ignores uppercase/lowercase differences (case-folding). GREP treats all letters a-z as being identical to the corresponding letters A-Z in all situations. -l List match files: Only the name of each file containing a match is printed. After GREP finds a match, it prints the file name and processing immediately moves on to the next file. -n Numbers: Each matching line that GREP prints is preceded by its line number. -o UNIX output format: Changes the output format of matching lines to support more easily the UNIX style of command-line piping. All lines of output are preceded by the name of the file that contained the matching line. -r Regular expression search: The text defined by searchstring is treated as a regular expression instead of as a literal string. -u Update options: GREP will combine the options given on the command line with its default options and write these to the GREP.COM file as the new defaults. (In other words, GREP is self-configuring.) This option allows you to tailor the default option settings to your own taste. -v Non-match: Only non-matching lines are printed. Only lines that do not contain the search string are considered to be non-matching lines. -w Word search: Text found that matches the regular expression will be considered a match only if the character immediately preceding and following cannot be part of a word. The default word character set includes A-Z, 9-0, and the underscore (_). An alternate form of this option allows you to specify the set of legal word characters. Its form is -w[set], where set is any valid regular expression set definition. If alphabetic characters are used to define the set, the set will automatically be defined to contain both the uppercase and lowercase values for each letter in the set, regardless of how it is typed, even if the search is case-sensitive. If the -w option is used in combination with the -u option, the new set of legal characters is saved as the default set. -z Verbose: GREP prints the file name of every file searched. Each matching line is preceded by its line number. A count of matching lines in each file is given, even if the count is zero. Remember that each of GREP's options is a switch: its state reflects the way you last "flipped" it. At any given time, each option can only be on or off. Each occurrence of a given option on the command line overrides its previous definition. For example, grep -r -i- -d -i -r- main( my*.asm Given this command line, GREP will run with the -d option on, the -i option on, and the -r option off. You can install your preferred default setting for each option in GREP.COM with the -u option. For example, if you want GREP to always do a verbose search (-z on), you can install it with the following command: grep -u -z 3. THE SEARCH STRING -------------------- The value of the search string defines the pattern GREP will search for. A search string can be either a regular expression or a literal string. In a regular expression, certain characters have special meanings: they are operators that govern the search. In a literal string, there are no operators; each character is treated literally. You can enclose the search string in quotation marks to prevent spaces and tabs from being treated as delimiters. Matches will not cross line boundaries (a match must be contained in a single line). An expression is either a single character or a set of characters enclosed in brackets. A concatenation of regular expressions is a regular expression. 4. OPERATORS IN REGULAR EXPRESSIONS ----------------------------------- When you use the -r option, the search string is treated as a regular expression (not a literal expression) and the following characters take on special meanings: ^ A circumflex at the start of the expression matches the start of a line. $ A dollar sign at the end of the expression matches the end of a line. . A period matches any character. * An expression followed by an asterisk wildcard matches zero or more occurrences of that expression. For example, in fo*, the * operates on the expression o; it matches f, fo, foo, and so on. (f followed by zero or more os), but doesn't match fa. + An expression followed by a plus sign matches one or more occurrences of that expression: fo+ matches fo, foo, and so on, but not f. [] A string enclosed in brackets matches any character in that string, but no others. If the first character in the string is a circumflex (^), the expression matches any character except the characters in the string. For example, [xyz] matches x, y, or z, while [^xyz} matches a and b, but not x, y, or z. You can specify a range of characters with two characters separated by a hyphen (-). These can be combined to form expressions (like [a-bd-z?] to match ? and any lowercase letter except c). \ The backslash escape character tells GREP to seach for the literal character that follows it. For example, \. matches a period instead of "any character." Note: Four of the previously described characters ($, ., *, and +) do not have any special meaning when used within a bracketed set. In addition, the character ^ is only treated specially if it immediately follows the beginning of the set definition (that is, immediately after the [). Any ordinary character not mentioned in the preceding list matches that character. (> matches >, # matches #, and so on.) 5. THE FILE SPECIFICATION ------------------------- The third item in the GREP command line is filespec, the file specification; it tells GREP which files (or groups of files) to search. filespec can be an explicit file name, or a generic file name incorporating the DOS ? and * wildcards. In addition, you can enter a path (drive and directory information) as part of filespec. If you give filespec without a path, GREP only searches the current directory. 6. GREP EXAMPLES ---------------- The following examples assume that all of GREP's options default to off: Example 1 --------- Command line: grep start: *.asm Matches: start: restart: Does not match: restarted: ClockStart: Files Searched: *.ASM in current directory. Note: By default, the search is case-sensitive. Example 2 --------- Command line: grep -r [^a-z]main\ *( *.asm Matches: main(i:integer) main(i,j:integer) if (main ()) halt; Does not match: mymain() MAIN(i:integer); Files Searched: *.ASM in current directory. Note: GREP searches for the word main with no preceding lowercase letters ([^a-z]), followed by zero or more occurrences of blank spaces (\ *), then a left parenthesis. Since spaces and tabs are normally considered to be command line delimiters, you must quote them if you want to include them as part of a regular expression. In this case, the space after main is quoted with the backslash escape character. You could also accomplish this by placing the space in double quotes [^a-z]main" "* Example 3 --------- Command line: grep -ri [a-c]:\\data\.fil *.asm *.inc Matches: A:\data.fil c:\Data.Fil B:\DATA.FIL Does not match: d:\data.fil a:data.fil Files Searched: *.ASM and *.INC in current directory. Note: Because the backslash and period characters (\ and .) usually have special meaning, if you want to search for them, you must quote them by placing the backslash escape character immediately in front of them. Example 4 --------- Command line: grep -ri [^a-z]word[^a-z] *.doc Matches: every new word must be on a new line. MY WORD! word--smallest unit of speech. In the beginning there was the WORD, and the WORD Does not match: Each file has at least 2000 words. He misspells toward as toword. Files Searched: *.DOC in the current directory. Note: This format basically defines how to search for a given word. Example 5 --------- Command line: grep -iw word *.doc Matches: every new word must be on a new line However, MY WORD! word: smallest unit of speech that conveys meaning. In the beginning there was the WORD, and the WORD Does not match: each document contains at least 2000 words! He seems to continually misspell "toward" as "toword." Files searched: *.doc in the current directory. Note: This format defines a basic "word" search. Example 6 --------- Command line: grep "search string with spaces" *.doc *.asm a:\work\myfile.* Matches: This is a search string with spaces in it. Does not match: THIS IS A SEARCH STRING WITH SPACES IN IT. This is a search string with many spaces in it. Files Searched: *.DOC and *.ASM in the current directory, and MYFILE.* in a directory called \WORK on drive A:. Note: This is an example of how to search for a string with embedded spaces. Example 7 --------- Command line: grep -rd "[ ,.:?'\"]"$ \*.doc Matches: He said hi to me. Where are you going? Happening in anticipation of a unique situation, Examples include the following: "Many men smoke, but fu man chu." Does not match: He said "Hi" to me Where are you going? I'm headed to the beach this Files Searched: *.DOC in the root directory and all its subdirectories on the current drive. Note: This example searches for the characters ,.:?' and " at the end of a line. Notice that the double quote within the range is preceded by an escape character so it is treated as a normal character instead of as the ending quote for the string. Also, notice how the $ character appears outside of the quoted string. This demonstrates how regular expressions can be concatenated to form a longer expression. Example 8 --------- Command line: grep -ild " the " \*.doc or grep -i -l -d " the " \*.doc or grep -il -d " the " \*.doc Matches: Anyway, this is the time we have do you think? The main reason we are Does not match: He said "Hi" to me just when I Where are you going? I'll bet you're headed to Files Searched: *.DOC in the root directory and all its subdirectories on the current drive. Note: This example ignores case and just prints the names of any files that contain at least one match. The three examples show different ways of specifying multiple options.