You need to reverse the meaning of a search you're performing with the grep command. For instance, you've been searching for pepperoni pizza orders like this:
grep pepperoni pizza-orders.txt
and now you need to find all orders that don't have pepperoni.
Just add the
-v switch to your
grep search command, like this:
grep -v pepperoni pizza-orders.txt
As shown in the documentation below, the
-v switch stands for "invert switch". I like to think of it as reversing the meaning of the search.
The grep man page
While I'm writing about the
grep command, I thought I'd go ahead and include the help documentation from the
grep man page:
Usage: grep [OPTION]... PATTERN [FILE] ... Search for PATTERN in each FILE or standard input. Example: grep -i 'hello world' menu.h main.c Regexp selection and interpretation: -E, --extended-regexp PATTERN is an extended regular expression -F, --fixed-strings PATTERN is a set of newline-separated strings -G, --basic-regexp PATTERN is a basic regular expression -P, --perl-regexp PATTERN is a Perl regular expression -e, --regexp=PATTERN use PATTERN as a regular expression -f, --file=FILE obtain PATTERN from FILE -i, --ignore-case ignore case distinctions -w, --word-regexp force PATTERN to match only whole words -x, --line-regexp force PATTERN to match only whole lines -z, --null-data a data line ends in 0 byte, not newline Miscellaneous: -s, --no-messages suppress error messages -v, --invert-match select non-matching lines -V, --version print version information and exit --help display this help and exit --mmap use memory-mapped input if possible Output control: -m, --max-count=NUM stop after NUM matches -b, --byte-offset print the byte offset with output lines -n, --line-number print line number with output lines --line-buffered flush output on every line -H, --with-filename print the filename for each match -h, --no-filename suppress the prefixing filename on output --label=LABEL print LABEL as filename for standard input -o, --only-matching show only the part of a line matching PATTERN -q, --quiet, --silent suppress all normal output --binary-files=TYPE assume that binary files are TYPE TYPE is 'binary', 'text', or 'without-match' -a, --text equivalent to --binary-files=text -I equivalent to --binary-files=without-match -d, --directories=ACTION how to handle directories ACTION is 'read', 'recurse', or 'skip' -D, --devices=ACTION how to handle devices, FIFOs and sockets ACTION is 'read' or 'skip' -R, -r, --recursive equivalent to --directories=recurse --include=PATTERN files that match PATTERN will be examined --exclude=PATTERN files that match PATTERN will be skipped. --exclude-from=FILE files that match PATTERN in FILE will be skipped. -L, --files-without-match only print FILE names containing no match -l, --files-with-matches only print FILE names containing matches -c, --count only print a count of matching lines per FILE -Z, --null print 0 byte after FILE name Context control: -B, --before-context=NUM print NUM lines of leading context -A, --after-context=NUM print NUM lines of trailing context -C, --context=NUM print NUM lines of output context -NUM same as --context=NUM --color[=WHEN], --colour[=WHEN] use markers to distinguish the matching string WHEN may be `always', `never' or `auto'. -U, --binary do not strip CR characters at EOL (MSDOS) -u, --unix-byte-offsets report offsets as if CRs were not there (MSDOS) `egrep' means `grep -E'. `fgrep' means `grep -F'. With no FILE, or when FILE is -, read standard input. If less than two FILEs given, assume -h. Exit status is 0 if match, 1 if no match, and 2 if trouble.
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