Is there any subtle difference between:




as a relative path?

  • file wont execute but ./file will however I don't think that is your question. – Jesse_b Aug 4 '17 at 15:56
  • 1
    It can be useful to include the ./ when the file you're referring to would otherwise be misunderstood as a commandline argument, such as in rm -who-uses-filenames-like-this vs rm ./-who-uses-filenames-like-this – n.st Aug 4 '17 at 16:02
  • A related question is unix.stackexchange.com/questions/261190 – JdeBP Aug 4 '17 at 16:39

When used as a command name in a shell or in the exec*p() libc functions, file would look-up file in $PATH (or for a shell, possibly invoke the built-in version, or function by that name), while ./file would run the one the current directory.

It's not that ./ triggers a special behaviour, it's just that if the command name doesn't contain any /, it does a $PATH lookup. ./cmd is the most obvious way to give a path to cmd that contains a /.

The ./ prefix is also commonly used to make sure a file name doesn't start with a problematic character for some commands.

For instance:

rm ./-f

removes -f, while rm -f would call rm with the -f option (rm -- -f would also work). Or:

cat ./-
awk '{print $1}' ./a==b.txt

where -- wouldn't help.

You find that as rm ./* or awk ... ./* in scripts where you don't know if the expansion of * would yield problematic characters.

  • Thanks for your answer, Stéphane Chazelas! I do wonder if there is anything related the $PATH when asking this question! – Marshall An Aug 4 '17 at 20:10
  • If so, can I assume that I should use "./file" in most cases to prevent misuse, misinterpretation, and security vulnerability, unless I have compelling reason to use "file"? – Marshall An Aug 4 '17 at 20:18

Yes. Several.

C library functions

As mentioned in another answer, the exec*p() family of library functions use whether the name contains a slash character as a test for whether path searching should be performed.

Further reading

Other things that search paths

Programs can of course do their own path searches outwith the C library. They might be searching for things other than to execute them. Or they might want slightly different behaviour to that of the C library functions, which has some little-known surprises to those not aware of what the POSIX standard mandates. So they implement their own searching code. Usually they will follow the conventions of the C library, and if the name contains a slash character they will just use the name as-is.

For example:

Shells that have CDPATH or cdpath mechanisms perform this sort of search, and have this behaviour. Here is the TENEX C shell:

~> set cdpath=(/usr /)
~> cd ./etc
./etc: No such file or directory.
~> cd etc

Filenames that begin with a minus sign

One of the ways of making sure that a filename that begins with a minus sign is not taken to be a command-line option is to prefix it with ./. For examples:

  • rm ./-rf is a filename, and rm -rf is a command-line option.
  • find ./-name wibble is scanning two directory trees and finding everything; whereas find -name wibble is scanning one directory tree and applying a pattern match.

Further reading

Commands where the command syntax makes this important

Sometimes the syntax of the command is defined such that something is only a filename at all if it begins with a full stop. Otherwise it is something else. In a way, this is a generalization of the minus sign as an option character convention.

For example:

With Dan Bernstein's multilog from daemontools, Bruce Guenter's multilog from daemontools-encore, the djbwares multilog, and Laurent Bercot's s6-log from s6, the command-line arguments are a logging script where the first letter of each argument indicates what kind of script command it is. To denote a log directory, one has to give a command string argument that starts with a slash or a full stop character. multilog ./t ./u means log to two directories; whereas multilog t ./u means log to one directory and prepend timestamps.


file will search in your PATH for the file.

./file will ignore the PATH and search in the current directory.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.