running script with ". " and with "source "

Question

1. I was wondering if the following two ways of running a bash script are equivalent?

   . ./myScript.sh
   
   source myScript.sh
   

2. Are they both running the content of the script instead of running the script, i.e. not creating a subshell for running the script?

Answer 1

1. They are equivalent in bash in that they do exactly the same thing. On the other hand, source is 5 characters longer and is not portable to POSIX-only shells or Bourne whereas . (dot) is, so I never bother using source.

2. That is correct - sourcing a file runs the commands in the current shell and it will affect your current shell environment. You can still pass arguments to the sourced file and bash will actually look in $PATH for the file name just like a normal command if it doesn't contain any slashes.

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Not related to the original question of . vs source, but in your example,

. ./myScript.sh 

is not identical to

source myScript.sh

because while . and source are functionally identical, myScript.sh and ./myScript.sh are not the same. Since ./myScript.sh contains a slash, it's interpreted as a path and the shell just uses ./myScript.sh. However, myScript.sh does not have a slash so the shell does a $PATH search for it first. This is the POSIX specified standard behavior for .. Most shells default to this although they may add extensions (such as searching in the current working directory after the path search) or options to change the behavior of ./source.

Answer 2

Yes, they are equivalent. There is no functional difference; . is just a builtin synonym for source.

_{(Edit: Apparently this is only true for bash and zsh. Some lighter shells don't have source, only . is specified by POSIX so ksh, dash, ash, etc. may not have source. See jw013's answer for info.)}