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3

As the question says, what is the difference between executing a script with source command and with . , i.e.:

source /some/script

and

. /some/script
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2 Answers

up vote 17 down vote accepted

source and . are synonymous in bash.

Update 9-5-2012

There seems to be much disbelief about this! For anyone who might like to verify that the commands are simply synonyms and nothing more: first download and extract the source code. Then examine the file, builtins/source.def. You will read that both of the built-in commands, source and ., use the very same function: source_builtin. The original question was, "What is the difference between source and . in BASH."

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where is this defined? I mean is . an alias for source or is this some thing else? – binW Feb 9 '11 at 18:26
exact same thing – user8290 Feb 9 '11 at 18:42
3  
@binW: . is the traditional source command, inherited from the ancient bourne shell. source is just a bash builtin that does exactly the same as ., presumably because it's more readable (a . alone may be hard to spot with a small font). You'll see help source and help . shows the same info. – geirha Feb 9 '11 at 23:56
1  
@binW: If you look in man bash and then search for source you'll see that source filename [arguments] is a synonym for . filename [arguments]. – Matthew Rankin Feb 17 '11 at 12:22
This actually contradicts what I see in this question: askubuntu.com/questions/182012/… – ysap Aug 30 '12 at 1:09
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up vote 7 down vote

. is synonymous with source in bash, but not in POSIX sh, so you should use . if your script is run by /bin/sh. Note that bash claims to run like POSIX sh when called as /bin/sh, but accepts source without complaint.

This behaviour has bitten me, scripts tested with bash as /bin/sh fail when run under ash, for example.

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1  
POSIX does not restrict the shell. POSIX just says; the shell shall support at least this and that feature. So a POSIX shell is free to implement additional features as long as the ones described by POSIX are implemented. When the shebang says #!/bin/sh you should never assume the shell supports anything but POSIX features though. pubs.opengroup.org/onlinepubs/9699919799/utilities/… – geirha Feb 9 '11 at 23:51
You may be affected by the order of looking names up: unix.stackexchange.com/q/17815/8250 – Lekensteyn Jul 16 '12 at 11:05
This answer helped me, since sh is often used in cron. – dfrankow Mar 8 at 14:25

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