Diff for "BashFAQ/067"

Differences between revisions 4 and 6 (spanning 2 versions)

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

There are a few ways to do this

   #POSIX
   read -r var << EOF
   $var 
   EOF

One can also achieve in bash (and ksh93) using a herestring

   # 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, using sed for instance:

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

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 6 as of 2008-07-04 09:01:07 → ⇥
  Size: 883
  Editor: pgas
  Comment: posix solution with a here string
-Deletions are marked like this.
+Additions are marked like this.
 Line 3:
-There are a few ways to do this -- none of them elegant.

First, the most portable way would be to use `sed`:
+There are a few ways to do this
-Line 8:
+Line 5:
-   # POSIX
   x=$(echo "$x" | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')
+   #POSIX
   read -r var << EOF
   $var 
   EOF
-Line 12:
+Line 11:
-One can also achieve the same goal using Bash builtins:
+One can also achieve in bash (and ksh93) using a herestring
-Line 17:
+Line 16:
-   while [[ $x = [[:space:]]* ]]; do x=${x#[[:space:]]}; done

   # And now trailing:
   while [[ $x = *[[:space:]] ]]; do x=${x%[[:space:]]}; done
+   read -r x <<< "$x"
-Line 23:
+Line 19:
-Of course, the preceding example is not optimal, because it removes one character at a time, in a loop (although it's good enough in practice for most purposes).  If you want something a bit fancier, there's a solution using [:glob:extglob]:
+There's also a solution using [:glob:extglob]:
-Line 39:
+Line 35:
-There are many, many other ways to do this.  These are not necessarily the best, but they're known to work.
+There are many, many other ways to do this, using sed for instance:  
{{{
   # POSIX
   x=$(echo "$x" | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')
}}}
These are not necessarily the best, but they're known to work.