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Shell Metacharacters
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Metacharacter |
Description |
Input/Output |
|
| < | Redirects input |
| > | Redirects output to a specified file. |
| << | Redirects input and specifies that the shell should read input up to a specified line. |
| >> | Redirects output and specifies that the shell should add output to the end of a file. |
| 2> | Redirects diagnostic output to a specified file. (Bourne shell only) |
| >! | Redirects output and specifies that if the noclobber variable is set (prevents the overwriting of files), it should be ignored so that the files can be overwritten. (C shell only) |
| >& | Redirects both diagnostic and standard output and appends them to a file (C and Korn shells only) |
| >>& | Redirects both diagnostic and standard output to the end of an existing file (C shell only) |
Expansion and subtitution |
|
| $ | Specifies variable substitution. (C shell only) |
| ! | Specifies history substitution (C shell only) |
| : | Preceeds substitution modifiers (C shell only) |
| ^ | Used in special kinds of history substitution. (C shell only) |
| ' | Specifies command substitution (C shell only) |
| ${...} | Specify variable substitution. (Bourne and Korn shells only) |
| % | Specify job number substitution. (Korn shell only) |
| ...' | Specify command output substitution. (Korn shell only) |
| '...' | Specifies command output substitution. (Bourne shell only) |
Syntactic |
|
| ; | Separates commands that should be executed sequentially. |
| | | Separates commands that are part of a pipeline. |
| && | Runs the next command if the current command succeeds |
| || | Runs the next command if the current command fails |
| ;; | Separates elements of a case construct. (Bourne and Korn Shells only) |
| & | Runs a command in the background. |
| ( ) | Groups commands to run as a separate process in a subshell. |
| { } | Groups commands without creating a subshell. (Korn shell only) |
Filename |
|
| / | Separates the parts of a file's path name. |
| ? | Matches any single character except a leading dot (.). |
| * | Matches any sequence of characters except a leading dot (.). |
| [ ] | Matches any of the enclosed characters. |
| ~ | Specifies home directory when used at the beginning of file names. (C and Korn shell only) |
Quotation |
|
| \ | Specifies that the following character should be interpreted litterally; that is, without special meaning to the shell. |
| '...' | Specifies that any of the enclosed characters (except for ' in Korn and C shells, and &' in Bourne shell) should be interpreted literally; that is, without their special meaning to the shell. |
| "..." | Provides a special form of quoting. Specifies that the $, `(grave accent), and \ characters keep their special meaning, while all other enclosed characters are interpreted literally; that is, without their special meaning to the shell. |
File Name |
Purpose of the File |
| .cshrc | Defines your C shell environment with the .login file. (Read each time you start a new shell) |
| default.DECterm | Stores customization information for DECterms. |
| .kshrc | Defines your Korn shell environment with the .profile file. (Read each time you start a new shell) |
| .login | Defines your C shell environment. (Read only when you log into the system) |
| .mh_profile | Defines the environment for MH. |
| .mailrc | Defines the environment for mailx (Mail) and mail (binmail). |
| .mwmrc | Defines workspace menus and key bindings. |
| .profile | Defines your Korn and Bourne shell environments. (Read only when you log into the system) |
| .X11Startup | Controls which applications are invoked when you start a workstation session. |
| .XDefaults | Records Session Manager customizations. |
Variable |
Description |
| HOME | Specifies the name of your login directory; the directory that is the current directory when you log in. |
| PATH | Specifies the directories through which your system searches to find and execute commands. |
| CDPATH | Specifies the directories that the cd command searches to find the specified argument to cd. |
| Specifies the path name of the file where your mail is deposited. | |
| MAILCHECK | Specifies in seconds how often the shell checks for mail (600 seconds is the default.) |
| SHELL | Specifies your default shell. |
| PS1 | Specifies the default Bourne shell prompt. The default value is $ (dollar sign). |
| PS2 | Specifies the secondary prompt string; the string that the shell displays when it requires more input after you enter a command line. |
| HISTFILE | Specifies the path name of the file that is used to store the command history. (Korn shell only) |
| EDITOR | Specifies the default editor for command line editing at the shell prompt and for filename completion. (Korn shell only) |
| FCEDIT | Specifies the default editor for the fc command. (Kornshell only) |
| HISTSIZE | Specifies the number of previously entered commands that are accessible by this shell. (Korn shell only) |
Variable |
Description |
| argv | Specifies the name of your login directory; the directory that is the current directory when you log in. |
| autologout | Specifies the directories through which your system searches to find and execute commands. |
| cwd | Specifies the directories that the cd command searches to find the specified argument to cd. |
| home | Specifies the path name of the file where your mail is deposited. |
| ignoreeof | Specifies in seconds how often the shell checks for mail (600 seconds is the default.) |
| cdpath | Specifies your default shell. |
| noclobber | Specifies the default Bourne shell prompt. The default value is $ (dollar sign). |
| notify | Specifies the secondary prompt string; the string that the shell displays when it requires more input after you enter a command line. |
| path | Specifies the path name of the file that is used to store the command history. (Korn shell only) |
| prompt | Specifies the default editor for command line editing at the shell prompt and for filename completion. (Korn shell only) |
| shell | Specifies the default editor for the fc command. (Korn shell only) |
| status | Specifies the number of previously entered commands that are accessible by this shell. (Korn shell only) |
Expression |
Rule |
0-9, A-Z, a-z, |
Matches itself. |
| . | Matches any single character. |
| \char | Matches the character following the backslash regardless of whether the character is a metacharacter. |
| * | Matches any number of occurrences of the preceding expression, including none. |
| [ chars ] | Matches any one of the characters within the brackets. Ranges of characters can be abbreviated. |
| ^ | Matches the beginning of a line when used at the beginning of an expression. When used as the first character inside brackets, excludes the bracketed characters from being matched. Otherwise, matches itself. |
| expr expr ... | Forms a compound expression that matches any string which matches the first simple expression, then the second, and so on. |
| .profile | Defines your Korn and Bourne shell environments. (Read only when you log into the system) |
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