grep, g – search a file for a pattern

grep [ –bchiLlnsv ] [ –e ] pattern | –f patternfile [ file ... ]
g [ flags ] pattern [ file ... ]

Grep searches the input files (standard input default) for lines that match the pattern, a regular expression as defined in regexp(6) with the addition of a newline character as an alternative (substitute for |) with lowest precedence. Normally, each line matching the pattern is `selected', and each selected line is copied to the standard output. The options are
c    Print only a count of matching lines.
h    Do not print file name tags (headers) with output lines.
e    The following argument is taken as a pattern. This option makes it easy to specify patterns that might confuse argument parsing, such as –n.
i    Ignore alphabetic case distinctions. The implementation folds into lower case all letters in the pattern and input before interpretation. Matched lines are printed in their original form.
l    (ell) Print the names of files with selected lines; don't print the lines.
L    Print the names of files with no selected lines; the converse of –l.
n    Mark each printed line with its line number counted in its file.
s    Produce no output, but return status.
v    Reverse: print lines that do not match the pattern.
f    The pattern argument is the name of a file containing regular expressions one per line.
b    Don't buffer the output: write each output line as soon as it is discovered.

Output lines are tagged by file name when there is more than one input file. (To force this tagging, include /dev/null as a file name argument.)

Care should be taken when using the shell metacharacters $*[^|()=\ and newline in pattern; it is safest to enclose the entire expression in single quotes '...'. An expression starting with '*' will treat the rest of the expression as literal characters.

G invokes grep with –n (plus aditional flags, if provided) and forces tagging of output lines by file name. If no files are listed, it searches all files matching *.b *.c *.C *.h *.l *.m *.asm *.cc *.cs *.lx *.cgi *.pl *.py *.tex *.ms *.java *.xy *.go *.goc


ed(1), awk(1), sed(1), sam(1), regexp(6)

Exit status is null if any lines are selected, or non–null when no lines are selected or an error occurs.