Linux - Newbie This Linux forum is for members that are new to Linux.
Just starting out and have a question?
If it is not in the man pages or the how-to's this is the place! |
Notices |
Welcome to LinuxQuestions.org, a friendly and active Linux Community.
You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!
Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.
Are you new to LinuxQuestions.org? Visit the following links:
Site Howto |
Site FAQ |
Sitemap |
Register Now
If you have any problems with the registration process or your account login, please contact us. If you need to reset your password, click here.
Having a problem logging in? Please visit this page to clear all LQ-related cookies.
Get a virtual cloud desktop with the Linux distro that you want in less than five minutes with Shells! With over 10 pre-installed distros to choose from, the worry-free installation life is here! Whether you are a digital nomad or just looking for flexibility, Shells can put your Linux machine on the device that you want to use.
Exclusive for LQ members, get up to 45% off per month. Click here for more info.
|
 |
05-09-2017, 06:30 PM
|
#1
|
LQ Newbie
Registered: May 2017
Posts: 3
Rep: 
|
A bash script that I'm trying to understand
Okay
Last edited by orri23; 05-09-2017 at 08:05 PM.
Reason: Solved
|
|
|
05-09-2017, 06:39 PM
|
#2
|
LQ Guru
Registered: Aug 2004
Location: Sydney
Distribution: Rocky 9.x
Posts: 18,443
|
He's trying to ensure var $fn actually has a non-empty value.
I recommend running it with debugging options thus
Code:
set -xv # this makes the parser show you exactly what its doing as it goes
read fn
while [ "a$fn" != "a" ]
do
basename "$fn"
read fn
done
|
|
|
05-09-2017, 06:47 PM
|
#3
|
LQ Guru
Registered: Nov 2008
Location: Pictland
Distribution: Linux Mint 21 MATE
Posts: 8,048
|
|
|
|
05-09-2017, 07:34 PM
|
#4
|
Member
Registered: Feb 2014
Location: Michigan
Distribution: Debian 10
Posts: 203
Rep: 
|
why not use the -z test?
Example:
Code:
#!/bin/sh
#
TEST_STRING="This has been a test"
echo "Test 1 String value is : " $TEST_STRING
if [ -z "$TEST_STRING" ]
then
echo "Test String is empty."
else
echo $TEST_STRING
fi
TEST_STRING=""
echo "Test 2 : Test String is empty "
if [ -z "$TEST_STRING" ]
then
echo "Test String is empty."
else
echo $TEST_STRING
fi
exit 0
Result:
~/Documents/Scripting $ ./test_string.sh
Test 1 String value is : This has been a test
This has been a test
Test 2 : Test String is empty
Test String is empty.
~/Documents/Scripting $
i just acquired a copy of Shell Scripting (Jason Cannon) (Amazon) which to me is very helpful. Lots of examples!
|
|
|
05-10-2017, 06:47 AM
|
#5
|
Moderator
Registered: Mar 2011
Location: USA
Distribution: MINT Debian, Angstrom, SUSE, Ubuntu, Debian
Posts: 9,968
|
@orri23, welcome to LQ.
Please do not edit your posts and remove content, especially the question or problem description. This thread is now ineffective because it makes no sense. Consider revising the original question to allow the thread to possibly be helpful to future solution seekers. Please do not repeat this behavior in the future, it doesn't help the site, it doesn't help all to increase their Linux knowledge, which is mainly why we are all here.
Best Regards,
- RT
|
|
|
05-10-2017, 08:52 AM
|
#6
|
LQ Guru
Registered: Sep 2013
Location: Somewhere in my head.
Distribution: Slackware (15 current), Slack15, Ubuntu studio, MX Linux, FreeBSD 13.1, WIn10
Posts: 10,342
|
Why not use -n test?
(code example taken from @mike acker, then fixed and modified to match test prams)
Code:
#!/bin/sh
#
TEST_STRING="This has been a test"
echo "Test 1 String value is : " $TEST_STRING
if [ -n "$TEST_STRING" ] ;
then
echo "$TEST_STRING"
else
echo "Test String is empty."
fi
TEST_STRING=""
echo "Test 2 : Test String is empty "
if [ -n "$TEST_STRING" ] ;
then
echo "$TEST_STRING"
else
echo "Test String is empty."
fi
exit 0
example
Code:
userx%slackwhere ⚡ ~ ⚡> testS="hite"
userx%slackwhere ⚡ ~ ⚡> [[ -n $testS ]] && echo "got string"
got string
7.3. Other Comparison Operators
Last edited by BW-userx; 05-10-2017 at 09:00 AM.
|
|
|
All times are GMT -5. The time now is 01:34 PM.
|
LinuxQuestions.org is looking for people interested in writing
Editorials, Articles, Reviews, and more. If you'd like to contribute
content, let us know.
|
Latest Threads
LQ News
|
|