Bash: Check for Empty Variable

Raymond P. Burkholder - Things I Do

Google Analytics

Google Custom Search


"... an engineer who is not only competent at the analytics and technologies of engineering, but can bring value to clients, team well, design well, foster adoptions of new technologies, position for innovations, cope with accelerating change and mentor other engineers" -- CACM 2014/12

Blog Content ©2022
Raymond Burkholder
All Rights Reserved

+1 (403) 633-7293
+1 (441) 705-7293
raymond@burkholder.net

Available for Contract Work:
* Linux: Debian
* Languages: C++, Python, Perl
* Android: SDK, NDK, Java, C++, Audio
* Virtualization: KVM, LXC, VirtualBox, libvirt, ProxMox VE
* Routing/Switching: FRFouting, Pimd, OpenvSwitch
* Security: nftables, StrongSwan
* Automation: PXEBoot, SaltStack, Vagrant
* Networks: BGP, OSPF, Multicast, VXLAN, TC
* C++ Libraries: Wt, Boost, wxWidgets, ChartDir, HDF5
* Cisco Routing, Switching, MPLS, VPLS, Firewall/VPN
* Network Monitoring: SNMP, Netflow, Nagios, Check_MK
* Database: Cassandra, PostgreSQL, Microsoft SQL

GitHub: rburkholder
LinkedIn
Twitter: @oneunified
Resume

Categories



All categories

Syndicate This Blog

Friday, October 23. 2015

Bash: Check for Empty Variable

When working with command line substitutions, one way to check for presence (or lack thereof) of a command line variable: 


if [ "x$1" == "x" ];then
...
fi

If it matches, then there was no command line variable, as in 'x matches x'.

Posted by
Raymond P. Burkholder
in Bash at 12:00 | Comments (0)
Trackbacks
Trackback specific URI for this entry
No Trackbacks
Comments
Display comments as (Linear | Threaded)
No comments
Add Comment
Standard emoticons like :-) and ;-) are converted to images.
E-Mail addresses will not be displayed and will only be used for E-Mail notifications.
To leave a comment you must approve it via e-mail, which will be sent to your address after submission.

To prevent automated Bots from commentspamming, please enter the string you see in the image below in the appropriate input box. Your comment will only be submitted if the strings match. Please ensure that your browser supports and accepts cookies, or your comment cannot be verified correctly.
CAPTCHA 1CAPTCHA 2CAPTCHA 3CAPTCHA 4CAPTCHA 5


 
   
 


Calendar

Back July '25 Forward
Mo Tu We Th Fr Sa Su
Thursday, July 10. 2025
  1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30 31      

Archives



Blog Links:
Open Access Journals
Linux Insides
Bit Twiddling
Frink
Quote Database
Nanex Research
Sergey Solyanik
Chris Donnan
BeyondVC
lifehacker
Ticker Sense
HeadRush
TraderFeed
The Daily WTF
Guy Kawaski
Steve Pavlina
Matt Cutts
Joel On Software
Julian Dunn
Steve Yegge
ZeroHedge

Reference
VIM Cheat Sheet
TMux Cheat Sheet
GDB Cheat Sheet
Git Branching