Using "set -u" can be nasty. It's a way to force you to declare all your variables before using them, which is good programming practice. Referencing any unset variable will force the script to exit.
Unfortuantely this means you cannot even test if a variable is set without making the shell blow up. In these cases I usually see some piece of code framed by "set +u" and "set -u" again, which is ugly. If you have "set -u" active, then you should reference any external variables of unknown state like this:
Code:
VALUE=${unknownvar:-}
The shell uses the above syntax to return a default value when "unknownvar" is not set or is null. Since the default value is omited, it returns null but does NOT cause the shell to exit.
Hi 2 all,
i have had AIX 7.2
:/# /usr/IBMAHS/bin/apachectl -v
Server version: Apache/2.4.12 (Unix)
Server built: May 25 2015 04:58:27
:/#:/# /usr/IBMAHS/bin/apachectl -M
Loaded Modules:
core_module (static)
so_module (static)
http_module (static)
mpm_worker_module (static)
... (3 Replies)
Hello.
System : opensuse leap 42.3
I have a bash script that build a text file.
I would like the last command doing :
print_cmd -o page-left=43 -o page-right=22 -o page-top=28 -o page-bottom=43 -o font=LatinModernMono12:regular:9 some_file.txt
where :
print_cmd ::= some printing... (1 Reply)
Look at the following data file（cou.data） which has four fields separated by tab.
Four fields are country name, land area, population, continent where it belongs.
As for country name or continent name which has two words, two words are separated by space.
(Data are not accurately... (1 Reply)
How to use "mailx" command to do e-mail reading the input file containing email address, where column 1 has name and column 2 containing “To” e-mail address
and column 3 contains “cc” e-mail address to include with same email.
Sample input file, email.txt
Below is an sample code where... (2 Replies)
Hi,
I have line in input file as below:
3G_CENTRAL;INDONESIA_(M)_TELKOMSEL;SPECIAL_WORLD_GRP_7_FA_2_TELKOMSEL
My expected output for line in the file must be :
"1-Radon1-cMOC_deg"|"LDIndex"|"3G_CENTRAL|INDONESIA_(M)_TELKOMSEL"|LAST|"SPECIAL_WORLD_GRP_7_FA_2_TELKOMSEL"
Can someone... (7 Replies)
Hi Friends,
Can any of you explain me about the below line of code?
mn_code=`env|grep "..mn"|awk -F"=" '{print $2}'`
Im not able to understand, what exactly it is doing :confused:
Any help would be useful for me.
Lokesha (4 Replies)
Hi,
Please clarify what is the difference between "env" and "set" command.
I guess set will display the system variables and user defined variables.
Thanks
Sweta (1 Reply)
Hi,
i'm programming on /bin/csh and i need to get the number extracted by this:
set ppl_kn = $(awk '{ field = $6 } ; END{ print field }' < ppl_LM_kn.ppl )
and the output is: "Illegal variable name."
Please anyone can help me what's wrong?
Thanks in advance (2 Replies)
