Shell – How to escape < or > in a parameter in shell

escape-charactersparameterquotingshell

I'd like to use grep with a PCRE expression that contains the < character. Bash thinks I want to redirect, but I don't want to. How can I escape <?

Best Answer

I was able to do it with a backslash:

25 % grep \< xmospos.c
#include        <stdio.h>
#include        <stdlib.h>
#include        <getopt.h>
#include        <X11/Xlib.h>

A quoted less-than, and a quoted, backslashed less than both gave goofy answers.

Related Solutions

Bash – Ignore escape characters when printing string in shell script

If the TeX you want to output is fixed in your script, the safest is to use something like this:

cat > $2.tex << 'ENDHEADER'
\documentclass{article}
 \usepackage[utf8x]{inputenc}
 \pagestyle{empty}
\begin{document}
\[
ENDHEADER
echo $1 >> $2.tex
cat >> $2.tex << 'ENDFOOTER'
\]
\end{document}
ENDFOOTER

The data between the cat and END markers will be output as is with no substitutions. (I'm assuming all the newlines added are ok.)

Make sure you use hard quotes (') when you pass your TeX as an argument:

./your_script '\left( \begin{array}{cc}1 & 2\\ 3 & 4\end{array} \right)'

Bash – How to Escape Quotes in the Bash Shell

You can use the following string literal syntax:

> echo $'\'single quote phrase\' "double quote phrase"'
'single quote phrase' "double quote phrase"

From `man bash`

Words of the form $'string' are treated specially. The word expands to string, with backslash-escaped characters replaced as specified by the ANSI C standard. Backslash escape sequences, if present, are decoded as follows:

          \a     alert (bell)
          \b     backspace
          \e
          \E     an escape character
          \f     form feed
          \n     new line
          \r     carriage return
          \t     horizontal tab
          \v     vertical tab
          \\     backslash
          \'     single quote
          \"     double quote
          \nnn   the eight-bit character whose value is the octal value nnn (one to three digits)
          \xHH   the eight-bit character whose value is the hexadecimal value HH (one or two hex digits)
          \cx    a control-x character

Best Answer

Related Solutions

Bash – Ignore escape characters when printing string in shell script

Bash – How to Escape Quotes in the Bash Shell

From man bash

Related Question

From `man bash`