Bash scripting tricks

Bash tricks

1. Check bash version in script

   if ((BASH_VERSINFO[0] < 4))
   then
    echo "Sorry, you need at least bash-4.0 to run this script."
    exit 1
   fi

    

2. Reading columns from a file in bash array

   table_collection=( $(cut -d $'\t' -f1 table_data.dat) )

   The above reads column 1 (f1 – field 1) in table_collection array

3. Compress individual files in a directory

   for i in *; do tar -czvf $i.tar.gz $i; done

    

4. Forward declaration in bash or shell script

   #!/bin/bash
   main() {
       foo
       bar
       baz
   }
   foo() {
   }
   bar() {
   }
   baz() {
   }
   main "$@"
   

   https://stackoverflow.com/questions/13588457/forward-function-declarations-in-a-bash-or-a-shell-script

5. Let screen load your .bash_profile
   Edit ~/.screenrc to contain

   shell -$SHELL

   this will make screen start-up using a login shell which will load your ~/.bash_profile
   https://superuser.com/questions/343541/how-to-force-gnu-screen-to-load-my-bash-profile

6. Coming soon…