what does " ||" mean? ( Double pipe)

Muktesh · #1 (**permalink**) 08-30-2007

I found a line in one of the shell scripts,

cd /tmp || exit 2

What does this double pipe "||" mean?

Can any one tell what it is doing?

Thanks in advance.

andryk · #2 (**permalink**) 08-30-2007

if the first command succeed the second will never be executed
Or
if the cd /tmp fails it will execute 'exit 2'

robotronic · #3 (**permalink**) 08-30-2007

If the exit status of the first command (cd /tmp) is not 0, then execute the second command (exit 2).
It's the opposite of '&&', where the second command is executed only if the exit status of the preceding command is 0.

For example:

Code:

$ ls this_file_does_not_exist.txt || echo KO
ls: cannot access this_file_does_not_exist.txt: No such file or directory
KO

$ ls this_file_exist.txt && echo OK
this_file_exist.txt
OK

car2nst2006 · #4 (**permalink**) 09-12-2007

Thery are both correct but i believe that you are looking for this:

the || in a script "shell or perl" refers to: OR.

|| is equal to OR

So all your scripts are saying do this || \ OR this

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