Here is the source Grep
setup a dir with a file named "file" with this content
1 This is a file
2
3
4 This is text
5
6
7
8
9
There is 3 main way to feed inputs in grep:
grep text file
Gives the line 4
grep -r text ./
Gives the line 4
cat file | grep text
Gives the line 4
grep -i this file
line 1 and 4 event if not capitalized
grep -v text file
every line but 4
grep -w tex file
nothing
grep -w text file
works
grep -x 1 file
nothing
grep -x "1 This is a file" file
works
grep -e file -e text file
gives line 1 and 4
grep -n text file
display line number in front of our actual line
grep -A1 text file
1 line after
grep -B2 text file
2 line before
grep -C3 text file
3 line before/after
grep -m1 This file
only the first "This"
grep -c This file
will give 2 because 2 "This in file"
grep -E t$ file
only 4 because end in "t"
useful when you pass grep to something else before printing.
grep --color=always useful info
did a mistake but ok (test)
Will print everything but color your search pattern.
grep "text\|$" file
The search text "search\|$" is actually a trick, it will match lines that have pattern OR lines that have an end. Because all lines have an end, all lines are matched, but the end of a line isn't actually any characters, so it won't be colored.[1]