## 6.3. Common Features

The following table is a sampling of features that are common to bash, csh, and tcsh. Note that tcsh is an enhanced version of csh; therefore, tcsh includes all features of csh, plus some others.

Symbol/Command | Meaning/Action
--- | ---
`>` | Redirect output.
`>>` | Append output to file.
`<` | Redirect input.
`<<` | ``Here'' document (redirect input).
`|` | Pipe output.
`&` | Run process in background.
`;` | Separate commands on same line.
`*` | Match any character(s) in filename.
`?` | Match single character in filename.
`!`n | Repeat command number n.
`[ ]` | Match any characters enclosed.
`( )` | Execute in subshell.
`` `` | Substitute output of enclosed command.
`" "` | Partial quote (allows variable and command expansion).
`\` | Quote following character.
`$`var | Use value for variable.
`$$` | Process ID.
`$0` | Command name.
`$`n | nth argument (0<n9).
`$*` | All arguments.
`#` | Begin comment.
`bg` | Background execution.
`break` | Break from loop statements.
`cd` | Change directories.
`continue` | Resume a program loop.
`echo` | Display output.
`eval` | Evaluate arguments.
`exec` | Execute a new shell or other program.
`fg` | Foreground execution.
`jobs` | Show active jobs.
`kill` | Terminate running jobs.
`newgrp` | Change to a new group.
`shift` | Shift positional parameters.
`stop` | Suspend a background job.
`suspend` | Suspend a foreground job.
`umask` | Set or list permissions on files to be created.
`unset` | Erase variable or function definitions.
`wait` | Wait for a background job to finish.

Copyright © 2001 O'Reilly & Associates. All rights reserved.