Shell features

There are advantages to using the shell as an interface to the system.

The primary advantages of interfacing to the system through a shell are as follows:

• Wildcard substitution in file names (pattern-matching)

  Carries out commands on a group of files by specifying a pattern to match, rather than specifying an actual file name.

  For more information, see:

  • File name substitution in the Korn shell or POSIX shell
  • File name substitution in the Bourne shell
  • File name substitution in the C shell
• Background processing

  Sets up lengthy tasks to run in the background, freeing the terminal for concurrent interactive processing.

  For more information, see the bg command in the following:

  • Job control in the Korn shell or POSIX shell
  • C shell built-in commands
    Note: The Bourne shell does not support job control.
• Command aliasing

  Gives an alias name to a command or phrase. When the shell encounters an alias on the command line or in a shell script, it substitutes the text to which the alias refers.

  For more information, see:

  • Command aliasing in the Korn shell or POSIX shell
  • Alias substitution in the C shell
    Note: The Bourne shell does not support command aliasing.
• Command history

  Records the commands you enter in a history file. You can use this file to easily access, modify, and reissue any listed command.

  For more information, see the history command in the following:

  • Korn shell or POSIX shell command history
  • C shell built-in commands
  • History substitution in the C shell
    Note: The Bourne shell does not support command history.
• File name substitution

  Automatically produces a list of file names on a command line using pattern-matching characters.

  For more information, see:

  • File name substitution in the Korn shell or POSIX shell
  • File name substitution in the Bourne shell
  • File name substitution in the C shell
• Input and output redirection

  Redirects input away from the keyboard and redirects output to a file or device other than the terminal. For example, input to a program can be provided from a file and redirected to the printer or to another file.

  For more information, see:

  • Input and output redirection in the Korn shell or POSIX shell
  • Input and output redirection in the Bourne shell
  • Input and output redirection in the C shell

• Piping

  Links any number of commands together to form a complex program. The standard output of one program becomes the standard input of the next.

  For more information, see the pipeline definition in Shells terminology.

• Shell variable substitution

  Stores data in user-defined variables and predefined shell variables.

  For more information, see:

  • Parameter substitution in the Korn shell or POSIX shell
  • Variable substitution in the Bourne shell
  • Variable substitution in the C shell