Nested for loop with output text variable

Question

I need to modify simple bash script to go through a files and add some text to the end of each file with name of the file variable. There's an example of Nagios .cfg file...so far I got something like this:

#!/bin/bash

list=$(ls /root/user/test/ | sed "s/\.cfg//")

for servery in `/root/user/test/*.cfg`; do
    for $list; do
        echo `
        
        define service {
               host_name                       $list
               service_description             All_fs_free_space
               check_command                   check_nrpe!check_all_disks!3% 1%
               use                             user-disk
        }` >> /etc/nagios3/conf.d/servers/test/$servery
    done
done

which unfortunately didn't work, because of quotation marks...? Is there better solution how to achieve that? Thank you.

Debug output for Paul Hodges solution:

    root@bla:~/blabla# ./add2.sh
    ++ fmt='
    
        define service {
               host_name                       %s
               service_description             All_fs_free_space
               check_command                   check_nrpe!check_all_disks!3%% 1%%
               use                             user-disk
        }'
    ++ for file in '/root/user/test/*.cfg'
    ++ cfg='*.cfg'
    ++ printf '
    
        define service {
               host_name                       %s
               service_description             All_fs_free_space
               check_command                   check_nrpe!check_all_disks!3%% 1%%
               use                             user-disk
        }' '*'
    ./add2.sh: line 14: /root/blabla/test/servers/$cfg: ambiguous redirect

Does this answer your question? Difference between single and double quotes in Bash — John Kugelman
– John Kugelman, Commented Jul 9, 2020 at 19:40
Run your script through Shell Check. You've got several simple syntax errors. — John Kugelman
– John Kugelman, Commented Jul 9, 2020 at 19:41
Pretty sure you don't want backticks around /root/user/test/*.cfg or your output. — Paul Hodges
– Paul Hodges, Commented Jul 9, 2020 at 20:38
++ for file in '/root/user/test/*.cfg' and ++ cfg='*.cfg' mean there are no filenames that end with cfg in /root/user/test/ for it to loop over. If you want that to skip the loop with no error (or any other useful output), set shopt -s nullglob. Otherwise, explicitly test for the existence of /root/blabla/test/servers/$cfg before processing, and fail out if it isn't there. See below. — Paul Hodges
– Paul Hodges, Commented Jul 27, 2020 at 13:48

Paul Hodges · Accepted Answer · 2020-07-27 13:50:37Z

1

Abstract it a bit more.

Update -

Checking for existence of file, as per comments above.

#!/bin/bash
fmt='

    define service {
           host_name                       %s
           service_description             All_fs_free_space
           check_command                   check_nrpe!check_all_disks!3%% 1%%
           use                             user-disk
    }'

for file in /root/user/test/*.cfg # assuming there are *.cfg files here
do if [[ -e "/root/blabla/test/servers/$cfg" ]]
   then cfg=${file##*/}                # stripping the path
        printf "$fmt\n" "${cfg%.cfg}" >> /etc/nagios3/conf.d/servers/test/$cfg
   else echo "File not found: /root/blabla/test/servers/$cfg" >&2
   fi
done

Making some assumptions about what you intended.
I'd back everything up first, and then edit to only match one file for a test before using wildcards...

edited Jul 27, 2020 at 13:50

answered Jul 9, 2020 at 20:55

Paul Hodges

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6 Comments

Jan Ves. Over a year ago

Yes, but this will probably do only part of the job. At the place "%s" ($list in my example) I need variable which contain name of the configuration file (host name of a server exactly) without cfg suffix. Skript with one iteration puts content of $fmt at the end of the file and changes variable $list like name of the file which will be modified.

Paul Hodges Over a year ago

%s is a string replacement indicator in the "$fmt" format string of the printf, which is why there's another argument - cfg=${file##*/} strips the leading path info off, so "${cfg%.cfg}" is just the name of the configuration file without the cfg suffix. Did you try it?

Jan Ves. Over a year ago

Oh ok sorry, I didn't know, bash magic. But anyway I got "line 13: /etc/nagios3/conf.d/servers/test/$cfg: ambiguous redirect"

Paul Hodges Over a year ago

Put a set -x at the top to see what's actually being parsed. Odd that the $cfg isn't being expanded first.

Jan Ves. Over a year ago

use user-disk }' '*' this is the two last lines of code before error with set -x

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