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Old 01-04-2008, 12:55 AM   #1
muazfarooqaslam
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Registered: Dec 2007
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Difference between executing & sourcing a script


Hi,

Can anybody please explain the difference between executing a script and sourcing a script and what is the purpose of both.

rgds
 
Old 01-04-2008, 02:51 AM   #2
matthewg42
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Registered: Oct 2003
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Distribution: Kubuntu 12.10 (using awesome wm though)
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If you execute a script by setting the executable permission and then calling it by it's full or relative path, or just by name if it is in the PATH, then a new shell process will be created to interpret the script (the shell type determined by the shebang line at the start of the script).

If you source a script either by using the source keyword or the . syntax, i.e. one of these:
Code:
source test.sh
. test.sh
...then the file will be read and executed in the current shell.

There are a few implications of using source over executing a script:
  • Environment variables and other shell variables which are set during the course of the script's run will still be available after the script's contents have completed running.
  • If you call exit from the sourced script, it will terminate the calling script / interactive shell.
  • You won't incur the overhead of starting a new shell process. For one-off calls this isn't so interesting, but if you want to execute a script many times in a loop it might make a useful difference.
 
  


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