I would like to control a bash script like this:


imapsync \
--buffersize 8192000 --nosyncacls --subscribe --syncinternaldates --IgnoreSizeErrors \
--host1 $HOST1 --user1 $USER1 --password1 $PW1 --ssl1 --port1 993 --noauthmd5 \
--host2 $HOST2 --user2 $USER2 --password2 $PW2 --ssl2 --port2 993 --noauthmd5 --allowsizemismatch

with parameters from a control file like this:

host1 user1 password1 host2 user2 password2
anotherhost1 anotheruser1 anotherpassword1 anotherhost2 anotheruser2 anotherpassword2 

where each line represents one run of the script with the parameters extracted and made into variables.

what would be the most elegant way of doing this?



With shell scripts, this is normally accomplished using the source function, which executes the file as a shell script as if it was inlined into the script you're running -- which means that any variables you set in the file are exported into your script.

The downside is that (a) your config file is executed, so it's a security risk if unprivileged users can edit privileged config files. And (b) your config file syntax is restricted to valid bash syntax. Still, it's REALLY convenient.





# Set defaults   

# Load config values
source config.conf

foobar2000 --user=$USER --pass=$PASS --HOST=$HOST

source can be abbreviated with a single . -- so the following two are equivalent:

 source file.sh
 . file.sh
  • 1
    I could be wrong, but I believe he wants to loop over options in a config file. I don't thing just using source will do what he wants. – Zoredache Jan 6 '11 at 8:51
  • Yeah, I thought of source too but I think he doesn't want it that way. – weeheavy Jan 6 '11 at 10:19
  • correct, the looping part is the important one, as i need to mass import some stuff.. – perler Jan 6 '11 at 15:18

Something like this. The important bit is using read to grab a line as an array.

cat $configfile | while read -a HR ; do

  [[ -z ${HR[0]} ]] && continue  # skip empty lines


  imapsync \
  --buffersize 8192000 --nosyncacls --subscribe --syncinternaldates --IgnoreSizeErrors \
  --host1 $HOST1 --user1 $USER1 --password1 $PW1 --ssl1 --port1 993 --noauthmd5 \
  --host2 $HOST2 --user2 $USER2 --password2 $PW2 --ssl2 --port2 993 --noauthmd5 --allowsizemismatch

  • 1
    +1 for making me look up the difference between [ and [[. (tldp.org/LDP/abs/html/testconstructs.html#DBLBRACKETS if the OP is interested.) Very useful. – SmallClanger Jan 6 '11 at 9:35
  • 2
    You could read directly into the variables: read -r USER1 HOST1 PW1 .... Note that -r should almost always be used (it allows backslashes to be read literally). Piping into while creates a subshell (which may not be a problem here). You can avoid that by redirecting the file into done: done < "$configfile". @SmallClanger: See also BashFAQ/031. – Dennis Williamson Jan 6 '11 at 16:33
  • @Dennis Williamson, of course you are right, but the above was what I already had in a working script, please excuse the slight laziness. :) – Zoredache Jan 6 '11 at 18:06
  • @Dennis Williamson - Ah, much clearer than the ABS. Thanks. Also, Ditto the read -r option. – SmallClanger Jan 6 '11 at 18:30
  • @Zoredache: like Dennis said, you should avoid the cat $configfile | while ... done by moving it over to while ..... done < "$configfile" so that all the variables you define or modify in the while are not just for the while's duration (if it is in a subshell) but exist after it as well. And it is one less "UUOC" (Useless Use Of Cat) – Olivier Dulac Apr 7 '16 at 6:06

I think you should be using something like getopts if you want to make your script intelligent, instead of just trying to read your arguments on the number basis.

Something like this.


while getopts ":a" opt; do
  case $opt in
      echo "-a was triggered!" >&2
      echo "Invalid option: -$OPTARG" >&2

$ ./go_test.sh -a
-a was triggered!

You can parse arguments also. You can read more details about the tutorial over here.

  • Needs improvements: a more robust example could be : OPTIND=1; SILENT=":"; while getopts "${SILENT}a:bc:" opt ; do case $opt in a) val=$OPTARG; ... ;; b) ... ;; c) val=$OPTARG; ... ;; :) echo "(silent mode): -${OP TARG} needs argument"; ... ;; ?) echo "(non-silent) : option not recognized"; ... ;; esac ; done ; shift $((OPTIND - 1)) . OPTIND is set to 1 so you can call the getopts multiple times if needed, and the shift makes sure you process the remaining args only. By default, processes the $1 ... $n, but can process other args if you put them after the "opt" and before the ";" above – Olivier Dulac Apr 7 '16 at 6:40

I found working solution here: https://af-design.com/2009/07/07/loading-data-into-bash-variables/

if [ -f "$SETTINGS_FILE" ];then

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