Diff for "BashFAQ/067"

Differences between revisions 4 and 5

How can I trim leading/trailing white space from one of my variables?

There are a few ways to do this -- none of them elegant.

First, the most portable way would be to use sed:

   # POSIX
   x=$(echo "$x" | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')

One can also achieve the same goal using Bash builtins:

   # Bash
   # Remove leading whitespace:
   read -r x <<< "$x"

There's also a solution using [:glob:extglob]:

   # Bash
   shopt -s extglob
   x=${x##+([[:space:]])} x=${x%%+([[:space:]])}
   shopt -u extglob

This also works in KornShell, without needing the explicit extglob setting:

   # ksh
   x=${x##+([[:space:]])} x=${x%%+([[:space:]])}

There are many, many other ways to do this. These are not necessarily the best, but they're known to work.

-  ⇤ ← Revision 4 as of 2008-05-21 20:52:00 → 
  Size: 1195
  Editor: GreyCat
  Comment: clean up
+   ← Revision 5 as of 2008-07-04 08:55:23 → ⇥
  Size: 871
  Editor: pgas
  Comment: remove the loop add a solution with read and here strings
-Deletions are marked like this.
+Additions are marked like this.
 Line 17:
-   while [[ $x = [[:space:]]* ]]; do x=${x#[[:space:]]}; done

   # And now trailing:
   while [[ $x = *[[:space:]] ]]; do x=${x%[[:space:]]}; done
+   read -r x <<< "$x"
-Line 23:
+Line 20:
-Of course, the preceding example is not optimal, because it removes one character at a time, in a loop (although it's good enough in practice for most purposes).  If you want something a bit fancier, there's a solution using [:glob:extglob]:
+There's also a solution using [:glob:extglob]: