4.13. grep with Options (UNIX and GNU)
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4.13. grep with Options (UNIX and GNU)The grep command has a number of options that control its behavior. Not all versions of UNIX support exactly the same options, so be sure to check your man pages for a complete list. The examples in this section use the following datafile , which is repeated periodically for your convenience.
Example 4.53.% grep n '^south' datafile 3:southwest SW Lewis Dalsass 2.7 .8 2 18 4:southern SO Suan Chin 5.1 .95 4 15 5:southeast SE Patricia Hemenway 4.0 .7 4 17 EXPLANATION The “n option precedes each line with the number of the line where the pattern was found, followed by the line. Example 4.54.% grep i 'pat' datafile southeast SE Patricia Hemenway 4.0 .7 4 17 EXPLANATION The “i option turns off case sensitivity. It does not matter if the expression pat contains any combination of upper- or lowercase letters . Example 4.55.% grep v 'Suan Chin' datafile northwest NW Charles Main 3.0 .98 3 34 western WE Sharon Gray 5.3 .97 5 23 southwest SW Lewis Dalsass 2.7 .8 2 18 southeast SE Patricia Hemenway 4.0 .7 4 17 eastern EA TB Savage 4.4 .84 5 20 northeast NE AM Main Jr. 5.1 .94 3 13 north NO Margot Weber 4.5 .89 5 9 central CT Ann Stephens 5.7 .94 5 13 EXPLANATION Here, the “v option prints all lines not containing the pattern Suan Chin . This option is used when deleting a specific entry from the input file. To really remove the entry, you would redirect the output of grep to a temporary file, and then change the name of the temporary file back to the name of the original file as shown here: grep -v 'Suan Chin' datafile > temp mv temp datafile Remember that you must use a temporary file when redirecting the output from datafile . If you redirect from datafile to datafile , the shell will "clobber" the datafile . (See "Redirection" on page 25.) Example 4.56.% grep l 'SE' * datafile datebook EXPLANATION The “l option causes grep to print out only the filenames where the pattern is found instead of the line of text. Example 4.57.% grep c 'west' datafile 3 EXPLANATION The “c option causes grep to print the number of lines where the pattern was found. This does not mean the number of occurrences of the pattern. For example, if west is found three times on a line, it only counts the line once.
Example 4.58.% grep w 'north' datafile north NO Margot Weber 4.5 .89 5 9 EXPLANATION The “w option causes grep to find the pattern only if it is a word, [a] not part of a word. Only the line containing the word north is printed, not northwest , northeast , etc.
Example 4.59.% echo $LOGNAME lewis % grep -i "$LOGNAME" datafile southwest SW Lewis Dalsass 2.7 .8 2 18 EXPLANATION The value of the shell ENV variable, LOGNAME , is printed. It contains the user 's login name. If the variable is enclosed in double quotes, it will still be expanded by the shell, and in case there is more than one word assigned to the variable, whitespace is shielded from shell interpretation. If single quotes are used, variable substitution does not take place; that is, $LOGNAME is printed. 4.13.1 GNU grep Options ExamplesIn addition to the options provided with UNIX grep , the GNU version provides options that further refine the output resulting from pattern searches. The examples in this section use the following datafile , repeated periodically for your convenience.
Example 4.60.% grep -V grep (GNU grep) 2.2 Copyright (C) 1988, 92, 93, 94, 95, 96, 97 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for EXPLANATION With the “V option, grep 's version and copyright information are listed. The version information should be included with any bug reports sent to the GNU Foundation. Example 4.61.1 % grep -2 Patricia datafile southwest SW Lewis Dalsass 2.7 .8 2 18 southern SO Suan Chin 5.1 .95 4 15 southeast SE Patricia Hemenway 4.0 .7 4 17 eastern EA TB Savage 4.4 .84 5 20 northeast NE AM Main Jr. 5.1 .94 3 13 2 % grep -C Patricia datafile southwest SW Lewis Dalsass 2.7 .8 2 18 southern SO Suan Chin 5.1 .95 4 15 southeast SE Patricia Hemenway 4.0 .7 4 17 eastern EA TB Savage 4.4 .84 5 20 northeast NE AM Main Jr. 5.1 .94 3 13 EXPLANATION
Example 4.62.% grep -A 2 Patricia datafile southeast SE Patricia Hemenway 4.0 .7 4 17 eastern EA TB Savage 4.4 .84 5 20 northeast NE AM Main Jr. 5.1 .94 3 13 EXPLANATION After a line matching Patricia is found, grep displays that line and the two lines after it. Example 4.63.% grep -B 2 Patricia datafile southwest SW Lewis Dalsass 2.7 .8 2 18 southern SO Suan Chin 5.1 .95 4 15 southeast SE Patricia Hemenway 4.0 .7 4 17 EXPLANATION After a line matching Patricia is found, grep displays that line and the two lines before ( preceding ) it. Example 4.64.% grep -b '[abc]' datafile 0:northwest NW Charles Main 3.0 .98 3 34 39:western WE Sharon Gray 5.3 .97 5 23 76:southwest SW Lewis Dalsass 2.7 .8 2 18 115:southern SO Suan Chin 5.1 .95 4 15 150:southeast SE Patricia Hemenway 4.0 .7 4 17 193:eastern EA TB Savage 4.4 .84 5 20 228:northeast NE AM Main Jr. 5.1 .94 3 13 266:north NO Margot Weber 4.5 .89 5 9 301:central CT Ann Stephens 5.7 .94 5 13 EXPLANATION With the “b option, grep prints the byte offset from the input file before each line of output. Instead of using the datafile for these next two examples, we'll use a file called negative to demonstrate the “e and “x options.
Example 4.65.1 % grep -e '-alF' negative -alF are options to the ls command 2 % grep --regexp=-40 negative -40 is cold. EXPLANATION
Example 4.66.% grep -x -e '-40 is cold.' negative -40 is cold. EXPLANATION With the “x option, grep will not match a line unless the search pattern is identical to the entire line. The “e is used to allow a dash as the first character in the search string. The remaining examples in this section use the following datafile .
Example 4.67.1 % cat repatterns western north 2 % grep -f repatterns datafile northwest NW Charles Main 3.0 .98 3 34 western WE Sharon Gray 5.3 .97 5 23 northeast NE AM Main Jr. 5.1 .94 3 13 north NO Margot Weber 4.5 .89 5 9 EXPLANATION
Example 4.68.1 % grep '[0-9]' datafile db datafile:northwest NW Charles Main 3.0 .98 3 34 datafile:western WE Sharon Gray 5.3 .97 5 23 datafile:southwest SW Lewis Dalsass 2.7 .8 2 18 datafile:southern SO Suan Chin 5.1 .95 4 15 datafile:southeast SE Patricia Hemenway 4.0 .7 4 17 datafile:eastern EA TB Savage 4.4 .84 5 20 datafile:northeast NE AM Main Jr. 5.1 .94 3 13 datafile:north NO Margot Weber 4.5 .89 5 9 datafile:central CT Ann Stephens 5.7 .94 5 13 db:123 2 % grep -h '[0-9]' datafle db northwest NW Charles Main 3.0 .98 3 34 western WE Sharon Gray 5.3 .97 5 23 southwest SW Lewis Dalsass 2.7 .8 2 18 southern SO Suan Chin 5.1 .95 4 15 southeast SE Patricia Hemenway 4.0 .7 4 17 eastern EA TB Savage 4.4 .84 5 20 northeast NE AM Main Jr. 5.1 .94 3 13 north NO Margot Weber 4.5 .89 5 9 central CT Ann Stephens 5.7 .94 5 13 123 EXPLANATION
Example 4.69.% grep -q Charles datafile or % grep --quiet Charles datafile % echo $status 0 EXPLANATION The quiet option suppresses any output from grep . It is used when the exit status is all that is needed. If the exit status is zero, grep found the pattern. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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