LITMIR.BIZ

      The results show a common default path for a regular Linux user. Directories in the path list are separated by colons. Most user commands that come with Linux are stored in the /bin, /usr/bin, or /usr/local/bin directories. The /sbin and /usr/sbin directories contain administrative commands (some Linux systems don't put those directories in regular users' paths). The last directory shown is the bin directory in the user's home directory (/home/chris/bin).

      Unlike some other operating systems, Linux does not, by default, check the current directory for an executable before searching the path. It immediately begins searching the path, and executables in the current directory are run only if they are in the PATH variable or you give their absolute (such as /home/chris/scriptx.sh) or relative (for example, ./scriptx.sh) address.

      The path directory order is important. Directories are checked from left to right. So, in this example, if there is a command called foo located in both the /bin and /usr/bin directories, the one in /bin is executed. To have the other foo command run, you either type the full path to the command or change your PATH variable. (Changing your PATH and adding directories to it are described later in this chapter.)

      Not all the commands you run are located in directories in your PATH variable. Some commands are built into the shell. Other commands can be overridden by creating aliases that define any commands and options that you want the command to run. There are also ways of defining a function that consists of a stored series of commands. Here is the order in which the shell checks for the commands you type: