Grep usage

grep.txt

grep <pattern> <file>
grep -Hsi <pattern> <dir>

flags:
-r - recursive(include subdirs)
-l - show only filenames where was found pattern
-H - show in which file was found row
-с - count of pattern matches
-v - show only non-matches
-i - ignore case
-n - add row number to output
-s - hide errors
-w - only full word match
-C <num> - rows arround
-A <num> - row down
-B <num> - row up
-E - regex matching

patterns:
'\<word_start'
'word_end\>'
'^line_start'
'line_end$'
"word[<start>-<end>]"
"word[^<uninclude>]"