Clever Geek Handbook

How to find out where a command was run from in linux

Suppose I ran a command in unix like ls

or rm

and the path variable is set below

PATH=$JAVA_HOME/bin:.:$ORACLE_HOME/bin:/sbin:/usr/sbin:/usr/bin:/usr/ccs/bin:$COBDIR/bin:/sbin:/bin:/usr/local/bin:/bin

How can we know that the command ls

started some path? ls

(just an example) can be in /sbin

as well/usr/bin

So, I would like to know where is he from?

I cannot afford to search the entire directory and know where the entire directory lies ls

. is there a direct search method ls

it worked with?

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3 answers


When you run an external command in bash, bash hashes that command to avoid having to look up the path twice. The command hash

can tell you which command was run. If the command has not been run within the hash, it will result in an error.

$ hash -t ls
-bash: hash: ls: not found

$ ls foo
$ hash -t ls
/bin/ls

It is useful to know how the commands differ hash

, which

and type

.



  • hash

    tells you which path / command was used / hashed. If your PATH or filesystem changes over a hash

    lifetime, it hash

    can tell you about the commands that happened before this change.
  • which

    is an external command that looks for a command in an environment variable PATH

    .
  • type

    is a built-in command that looks for a command in a local variable PATH

    that may (but hardly ever) be different from that in the environment.

For details on how this works, see help hash

bash.

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Just use to find exactly where it will be picked up from

$ which ls
  /bin/ls


It will list to which path he chose this executable file. So from the above command, my ls command is in the / bin directory.

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In addition to other responses, which are referred to which

, type

, hash

, you can also use the the whereis (1) (if installed on your system).

whereis

tells you the standard places where the team should be.

If your interactive shell is zsh , you can also use a word =ls

like. echo =ls

or ls =ls

to see which one is ls

referring to the shell.

And you can also use an alias ls

or have a shell function ls

masquarading the executable /bin/ls

, etc. Of course, programs can run /bin/ls

without wrapping (e.g. using plain fork

+ execve

...)

Read also execvp (3) and environment (7)

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