Question

I wrote a short bash script that is supposed to strip the leading tabs/spaces from a string:

#!/bin/bash
RGX='s/^[ \t]*//'
SED="sed '$RGX'"
echo "       string" | $SED

It works from the command line, but the script gets this error:

sed: -e expression #1, char 1: unknown command: `''

My guess is that something is wrong with the quotes, but I’m not sure what.

Answer 1

It does. Try:

#!/bin/bash
RGX='s/^[ \t]*//'
#SED='$RGX'
echo "       string" | sed "$RGX"

This works.

The issue you have is with quotes and spaces. Double quoted strings are passed as single arguments.