linux - What is the difference between unlink and rm?

Is unlink any faster than rm?

Answer

Both are a wrapper to the same fundamental function which is an unlink() system call.

To weigh up the differences between the userland utilies.

rm(1):

• More options.



• More feedback.


• Sanity checking.


• A bit slower for single calls as a result of the above.


• Can be called with multiple arguments at the same time.

unlink(1):

• Less sanity checking.



• Unable to delete directories.


• Unable to recurse.


• Can only take one argument at a time.


• Marginally leaner for single calls due to it's simplicity.


• Slower when compared with giving rm(1) multiple arguments.

You could demonstrate the difference with:

$ touch $(seq 1 100)

$ unlink $(seq 1 100)
unlink: extra operand `2'

$ touch $(seq 1 100)
$ time rm $(seq 1 100)

real    0m0.048s
user    0m0.004s
sys     0m0.008s


$ touch $(seq 1 100)
$ time for i in $(seq 1 100); do rm $i; done

real    0m0.207s
user    0m0.044s
sys     0m0.112s

$ touch $(seq 1 100)
$ time for i in $(seq 1 100); do unlink $i; done


real    0m0.167s
user    0m0.048s
sys     0m0.120s

If however we're talking about an unadulterated call to the system unlink(2) function, which I now realise is probably not what you're accounting for.

You can perform a system unlink() on directories and files alike. But if the directory is a parent to other directories and files, then the link to that parent would be removed, but the children would be left dangling. Which is less than ideal.

Edit:

Sorry, clarified the difference between unlink(1) and unlink(2). Semantics are still going to differ between platform.