Help with for loop syntax

[bmead]

Howdy, I'm a total newbie to scripting and I can't figure out the proper syntax to shell script a for loop for the following scenario: I have a directory of symbolic links to backup log files. I want to loop through the dir to cat the last 21 lines of each file and put all the output to another file. I can't seem to get the loop to do what I want no matter how many different iterations of cat list | tail -21 etc. I try. I've looked through all my available books and on the web but so far no luck in finding just the right combo. Many thanks in advance for any help.

[masijade]

try it, post it, and we will help to correct it

[Salem]

First off, which "shell" are you talking about?
There are many varieties (sh, bash, ksh, csh) and syntax varies.

Maybe for i in `cat list`; do tail -21 $i; done

[JeoSaurus]

If all that's in that directory is the sym links to the files that you want to tail, try something like this: for i in $(ls /path/to/directory); do tail -n 21 $i; done Let us know how it goes! If we're missing the gist of what you're trying to do, post your script for us so that we can get a better idea!

Hope this helps!
-G

[bmead]

Thanks Salem, got an error (invalid option --2) when I tried yours - using sh as my shell. Masijade, here's what I've tried:

list=ls
for list
do 'cat list' | tail -21 > logfile
done

[Salem]

list in my example was a file, not a command.

> I want to loop through the dir to cat the last 21 lines of each file and put all the output to another file for i in *; do tail -21 $i; done Or begin with for i in *; do echo $i; done just to see what the for loop would use for filenames

[bmead]

Thanks all. Gromit's code suggestion works, I appended an output to a file ( > logfile) at the end to store the results for later viewing. I wanted to be able to identifiy each of the 21 line entries outputted according to its sym link (the server where it originated) so I also added an echo $i as:

for i in $(ls /path/to/directory); do tail -n 21 $i; echo $i; done > logfile

Thanks again for all your help!!