Solved

shell script

Posted on 2011-09-29
1
225 Views
Last Modified: 2012-05-12
what is the meaning of below .. pls give me some examples to understand better

        if [ x$TEMP_LIFE != "x" ]
0
Comment
Question by:damodar4u
1 Comment
 
LVL 11

Accepted Solution

by:
tel2 earned 500 total points
ID: 36841700
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

Highfive + Dolby Voice = No More Audio Complaints!

Poor audio quality is one of the top reasons people don’t use video conferencing. Get the crispest, clearest audio powered by Dolby Voice in every meeting. Highfive and Dolby Voice deliver the best video conferencing and audio experience for every meeting and every room.

Join & Write a Comment

Suggested Solutions

There are many situations when we need to display the data in sorted order. For example: Student details by name or by rank or by total marks etc. If you are working on data driven based projects then you will use sorting techniques very frequently.…
In the distant past (last year) I hacked together a little toy that would allow a couple of Manager types to query, preview, and extract data from a number of MongoDB instances, to their tool of choice: Excel (http://dilbert.com/strips/comic/2007-08…
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…
Internet Business Fax to Email Made Easy - With eFax Corporate (http://www.enterprise.efax.com), you'll receive a dedicated online fax number, which is used the same way as a typical analog fax number. You'll receive secure faxes in your email, fr…

708 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

17 Experts available now in Live!

Get 1:1 Help Now