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$ cat file
anna
amma
kklks
ksklaii
$ grep '\`' file
anna
amma
kklks
ksklaii
Why? How is that match working ?
640
The grep command (short for Global Regular Expressions Print) is a powerful text processing tool for searching through files and directories. When grep is combined with regex (regular expressions), advanced searching and output filtering become simple.
If you don't actually need to match the backtick itself, but you are looking to match something enclosed by a backtick ( like auto-generated MySQL table names, for instance) a single-character wildcard (".") also does the trick.
To display only the lines that do not match a search pattern, use the -v ( or --invert-match ) option. The -w option tells grep to return only those lines where the specified string is a whole word (enclosed by non-word characters). By default, grep is case-sensitive.
To use negative matching in grep , you should execute the command with the -v or --invert-match flags. This will print only the lines that don't match the pattern given.
This appears to be a GNU extension for regular expressions. The backtick ('\`') anchor matches the very start of a subject string, which explains why it is matching all lines. OS X apparently doesn't implement the GNU extensions, which would explain why your example doesn't match any lines there. See http://www.regular-expressions.info/gnu.html
If you want to match an actual backtick when the GNU extensions are in effect, this works for me:
grep '[`]' file
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