unix path guide

url link:http://stackoverflow.com/questions/221185/how-to-run-c-c-in-a-unix-console-mac-terminal

All application execution in a Unix (Linux, MacOS X, AIX etc) environment depends on the executable search path.

You can display this path in the terminal with this command:

echo $PATH

On MacOS X (by default) this will display the following colon separated search path:

/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin

So any executable in the listed directories can by run just by typing in their name. Eg:

cat mytextfile.txt

This runs /bin/cat and displays mytextfile.txt to the terminal.

To run any other command that is not in the executable search path requires that you qualify the path to the executable. So say I had an executable called MyProgram in my home directory on MacOS X I can fully qualify it like so:

/Users/oliver/MyProgram

If you are in a location that is near the program you wished to execute you can qualify the name with a partial path. For example if MyProgram was in the directory /Users/oliver/MyProject I and I was in my home directory I can qualify the executable name like this, and have it execute:

MyProject/MyProgram

Or say I was in the directory /Users/oliver/MyProject2 and I wanted to execute /Users/oliver/MyProject/MyProgram I can use a relative path like this, to execute it:

../MyProject/MyProgram

Similarly if I am in the same directory as MyProgram I need to use a "current directory" relative path. The current directory you are in is the period character followed by a slash. Eg:

./MyProgram

To determine which directory you are currently in use the pwd command.

If you are commonly putting programs in a place on your hard disk that you wish to run without having to qualify their names. For example if you have a "bin" directory in your home directory for regularly used shell scripts of other programs if may be wise to alter your executable search path.

This can be does easily by either creating or editing the existing .bash_profile file in your home directory and adding the lines:

#!/bin/sh
export PATH=$PATH:~/bin

Here the tilde (~) character is being used as a shortcut for /Users/oliver. Also note that the hash bang (#!) line needs to be the first line of the file (if it doesn't already exist). Note also that this technique requires that your login shell be bash (the default on MacOS X and most Linux distributions). Also note that if you want your programs installed in ~/bin to be used in preference to system executables your should reorder the export statement as follows:

export PATH=~/bin:$PATH