grep, g – search a file for a pattern

grep [ option ... ] pattern [ file ... ]
g [ option ... ] pattern [ file ... ]

Grep searches the input files (standard input default) for lines that match the pattern, a regular expression as defined in regexp(7) 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 and forces tagging of output lines by file name. If no files are listed, it searches all files matching
*.C *.b *.c *.h *.m *.cc *.java *.cgi *.pl *.py *.tex *.ms


ed(1), awk(1), sed(1), sam(1), regexp(7)

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

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