bourne / csh while differences

vellance · 01-11-2012, 12:15 PM

Hi,

I hope this belongs in the "Programming" section (I'm new to LQ)....

I am a junior FreeBSD sysadmin and really like csh (standard shell on our FreeBSD machines). Sometimes the need for a while loop arises. These last couple of weeks I have been forced to do certain stuff in bourne shell because my csh skills are not op to the task. This is a bit cumbersome and frustrating: how difficult can csh's while implementation be ?

I've searched a lot of websites (including LQ) but haven't been able to translate a simple while loop into correct csh syntax. Csh seems a bit elusive

Example:

file "kwaak.txt" contains :

a
b
c
1
2
3

I'm able to do stuff for each entry in bourne by issuing:

cat kwaak.txt | while read example ; do echo "Displaying $example" ; done

Output:

Displaying a
Displaying b
Displaying c
Displaying 1
Displaying 2
Displaying 3

If I issue the same command while in csh things obviously don't work because of the different syntax that is required by csh. After asking several coworkers and abusing google for quite some time I haven't been able to find the correct csh syntax.

My solution now is to enter a traditional bourne shell and do it there or to write a script that does it; both are not ideal.

Perhaps somebody on this forum can help out?

Any help would be greatly appreciated!

Regards,

FuX

colucix · 01-11-2012, 04:54 PM

Hi FuX and welcome to LinuxQuestions!

Reading a file line-by-line is one of the Top 10 reasons not to use the C-shell. Furthermore, you cannot feed a while loop with input from a pipe or from input redirection, since the if/while/foreach construct - and even the read statement - expect the standard input always from outside the script.

Anyway - you're lucky - a simple solution exists:

Code:

#!/bin/csh
foreach example (`cat kwaak.txt`)
  echo "Displaying $example"
end

Hope this helps.

vellance · 01-17-2012, 04:35 AM

Hi colucix,

TnX for your quick and helpfull reply. While your syntax is correct it seems only usable in shell scripts; the thing I wanted to avoid. TnX for the correct syntax though; might prove to be handy in the future

The link/info you provided made me "give up" on csh. I've accepted that for more complex stuff it is not suitable/ideal. I'm currently devising a way to

- log onto our machines and use /bin/sh instead of /bin/csh
- forward my ".shrc" over the ssh-connection to our machines

so that I don't have to work with csh anymore.

Thank you for your help!

Regards,

FuX