Search file(s) for lines that match a fixed string
It’s a popular fallacy that fgrep stands for fast-grep, in fact fgrep means fixed-string grep.
fgrep implements the Aho–Corasick string matching algorithm which is very fast at matching multiple strings in the input stream/file. So if fgrep is used like this:
fgrep -f patternlist.txt
it is much faster than
grep -f patternlist.txt largetextfile.txt
Matching a single pattern with fgrep is not significantly faster than grep.
Related linux commands:
egrep – Search file(s) for lines that match an extended expression
gawk – Find and Replace text within file(s)
grep – Search file(s) for lines that match a given pattern
Equivalent Windows command: FINDSTR – Search for strings in files