• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 236
  • Last Modified:

shell script

what is the meaning of below .. pls give me some examples to understand better

        if [ x$TEMP_LIFE != "x" ]
0
damodar4u
Asked:
damodar4u
1 Solution
 
tel2Commented:
This is not Perl, so this should be in a shell scripting zone.

This code:
    if [ x$TEMP_LIFE != "x" ]
is another way of writing:
    if [ $TEMP_LIFE != "" ]
(i.e. $TEMP_LIFE is not empty), but the latter would fail, because if $TEMP_LIFE is empty, it's like writing this:
    if [   != "" ]
which is a syntax error, because the != operator requires 1 argument on each side.
But if you prefix both with some character like "x", then if $TEMP_LIFE is empty, then it would be like writing this:
    if [ "x" != "x" ]
which works fine.

There are tidier ways to achieve the same, e.g.
    if [ "$TEMP_LIFE" != "" ]
or:
    if [ ! -z $TEMP_LIFE ]
To see what the -z switch means, do: man test
0

Featured Post

Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now