Читать книгу Linux Bible - Christopher Negus - Страница 95

Sometimes, you run a command and receive an error message that the command was not found or that permission to run the command was denied. If the command was not found, check that you spelled the command correctly and that it is located in your PATH variable. If permission to run the command was denied, the command may be in the PATH variable but may not be executable. Also remember that case is important, so typing CAT or Cat will not find the cat command.

If a command is not in your PATH variable, you can use the locate command to try to find it. Using locate, you can search any part of the system that is accessible to you. (Some files are only accessible to the root user.) For example, if you wanted to find the location of the chage command, you could enter the following:

 $ locate chage /usr/bin/chage /usr/sbin/lchage /usr/share/man/fr/man1/chage.1.gz /usr/share/man/it/man1/chage.1.gz /usr/share/man/ja/man1/chage.1.gz /usr/share/man/man1/chage.1.gz /usr/share/man/man1/lchage.1.gz /usr/share/man/pl/man1/chage.1.gz /usr/share/man/ru/man1/chage.1.gz /usr/share/man/sv/man1/chage.1.gz /usr/share/man/tr/man1/chage.1.gz

Notice that locate not only found the chage command, it also found the lchage command and a variety of man pages associated with chage for different languages. The locate command looks all over your filesystem, not just in directories that contain commands. (If locate does not find files recently added to your system, run updatedb as root to update the locate database.)

In the coming chapters, you learn to use additional commands. For now, I want you to become more familiar with how the shell itself works. So next I discuss features for recalling commands, completing commands, using variables, and creating aliases.