grep: Trailing backslash

Question

I want to do a grep for \resources\. How do I do this?

I've tried:

grep \resources\
grep \\resources\\
grep "\resources\"
grep "\\resources\\"

None of these work.

Answer 1

The backslash is a special character for many applications:

• including the shell: you need to escape it using another backslash or more elegantly, using single quotes when possible:

  $ printf '%s\n' foo\\bar 'foo\bar'
  foo\bar
  foo\bar
  

  Here the command received two arguments with value foo\bar, which were echoed as-is on the terminal.

  (Above, I used printf instead of echo as many echo implementations also do their own interpreting of backslash (here would expand \b into a backspace character)).

• But backslash is also a special character for grep. This command recognizes many special sequences like \(, \|, \., and so on. So similarly you need to feed grep with a double \\ for an actual backslash character. This means that using the shell you need to type:

  grep 'foo\\bar'
  

  or equivalently:

  grep foo\\\\bar
  

  (both lines tell the shell to transmit foo\\bar as argument to grep).

• Many other commands interpret backslashes in some of their arguments… and two levels of escaping are needed (one to escape the shell interpretation, one to escape the command interpretation).

---

By the way, for the shell, single quotes '…' prevent any kind of character interpretation, but double quotes only prevents some of them: in particular $, ` and \ remain active characters within "…".

Answer 2

You can also use fgrep (which is just grep with the -F flag). This forces grep to interpret the pattern as a fixed string (i.e. it'll treat a \ as a literal \). You'll still need to protect the backslashes from expansion by the shell.

grep -F '\resources\'

Answer 3

grep requires four backslashes to represent a backslash:

grep "\\\\resources\\\\"