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I am looking for lines that literally have a greater than character (a ">") followed by a space followed by a backslash character (a "\") i.e., a line with this: > \

I thought escaping would allow this, and for the greater-than it does:

  $ ack-grep "\> "

returns lines that have "> " in them.

But when I try to escape the backslash as well I get:

  $ ack-grep "\> \\"

ack-grep: Invalid regex '\> \':
Trailing \ in regex m/\> \/

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4 Answers 4

Wow, I was so close ... single quotes:

$ ack-grep '\> \\'

Figured this out after confirming that my regex match was valid using: http://regexpal.com/ and just happened to have had single quotes from trying something else.

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This also works:

$ ack-grep '> \\'

and so does:

$ ack-grep "> \\\\"

The greater-than doesn't need to be escaped.

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Please note that the issue here is not with ack but with the shell quoting. You'd have this problem with any program that you were trying to pass in "> \" as an argument.

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Yup, had I known this first: mpi-inf.mpg.de/~uwe/lehre/unixffb/quoting-guide.html 3.1.11 The golden rules of Bourne shell quoting Everything else that might be maltreated by the shell is protected by single quotes. –  Stephen Gornick Jun 1 '10 at 16:00

To search literal strings, use the literal option:

ack-grep --literal '> \'
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