|
HISTORY SUBSTITUTION
History substitution allows previous commands to be modified and re-executed. The history variable specifies the number of previous commands accessible in the current shell. The savehist variable specifies the number of commands to save in the ~/.history file between login sessions.
Format: event:word:modifiers
| event
| previous command from history file:
|
|
| !n
| command n
|
|
| !–n
| nth last command
|
|
| !string
| command that begins with string
|
|
| !?string
| command that contains string
|
|
| !!
| previous command
|
|
| !{...}
| separate history substitution from adjacent characters
|
|
| ^x^y
| substitute x for y on previous command line
|
| word
| individual word from previous command (: can be omitted if word begins with ^, $, *, –, or %).
|
|
| #
| entire command line
|
|
| 0
| first word
|
|
| n
| nth argument
|
|
| ^
| first argument
|
|
| $
| last argument
|
|
| %
| word matched by last ?string search
|
|
| x–y
| range of words from x to y
|
|
| –y
| range of words from first to y
|
|
| *
| all arguments (no match if only one word)
|
|
| x–
| range of words x to second to last argument
|
| modifier
| controls command/word selection (multiple modifiers must be separated with a : character). If prefixed with g, then the modification is applied to all arguments.
|
|
| e
| return filename suffix of first argument
|
|
| h
| return root pathname part of first argument
|
|
| p
| display new command, but do not execute
|
|
| q
| quote substituted words to prevent further substitution
|
|
| r
| return filename prefix of first argument
|
|
| s/x/y
| substitute first occurrence of x for y
|
|
| t
| return tail pathname part of first argument
|
|
| x
| same as q, except quote words individually
|
|
| &
| repeat previous substitution
|
FILENAME SUBSTITUTION
Unquoted words containing any of the following characters are expanded to a sorted list of filenames from the current directory. The “.” and “/” characters must be explicitly matched.
Pattern-Matching Characters
|
| ?
| match any single character
|
|
| *
| match zero or more characters
|
|
| [abc]
| match any characters between the brackets
|
|
| [x–z]
| match any character or characters in the range x to z
|
|
| [a–ce–g]
| match any characters in the range a to c, e to g
|
|
| {s1, s2, ...}
| match any string in the given set
|
|
| ~
| substitute the home directory of the invoker
|
|
| ~user
| substitute the home directory of user
|
JOB CONTROL
Job control is a process manipulation feature that allows programs to be stopped and restarted, moved between the foreground and background, their processing status to be displayed, and more. When a program is run in the background, a job number and process id are returned. Jobs being executed in the background will stop and notify you if they attempt to read input from the terminal. If notify is set, the Bourne shell will immediately notify you of blocked jobs.
Job Control Commands
| bg [%n]
| put current or stopped job n in the background
|
| fg [%n]
| move current or background job n into foreground
|
| jobs
| display the status of all jobs
|
| jobs –l
| display status of all jobs along with their process ids
|
| kill [–signal] [%n | PID]
| send signal to job n, current job, or specified process-ID (default TERM)
|
| kill –l
| list all valid signal names
|
| notify [%n]
| notify user when status of current job or job n changes
|
| stop [%n]
| stop current or specified job n
|
| stty [–]tostop
| allow/prevent background jobs from generating output
|
| suspend
| suspend execution of the current shell
|
| wait
| wait for all background jobs to complete
|
| Ctl-z
| stop the current job
|
Job Name Format
| %, %%, %+
| current job
|
| %n
| job n
|
| %–
| previous job
|
| %string
| job whose name begins with string
|
| %?string
| job that matches part or all of string
|
QUOTING
Quotes are used when assigning values containing whitespace or special characters, to delimit variables, and to assign command output.
| '...'
| remove the special meaning of enclosed characters except '
|
| "..."
| remove the special meaning of enclosed characters except $, ', !, and \
|
| \c
| remove the special meaning of character c
|
| `command
| replace with the standard output of command
|
VARIABLES
Like in other high-level programming languages, variables are used by the C shell to store values. Variable names can begin with an alphabetic or underscore character, followed by one or more alphanumeric or underscore characters. Variable names that contain only digits or special characters are reserved for special variables set directly by the C shell.
Variable Assignment Format
| set variable
| set variable to null
|
| set variable=value
| set variable to value
|
| set variable=(value1 value2 . . . valuen)
| set variable to value1 through valuen
|
| set variable[n]=value
| set variable element n to value
|
| set variable[n]=(value1 value2 . . . valuen)
| set variable element n to value1 through valuen
|
| unset variable
| remove the definition of variable
|
| @ variable=expression
| set variable to numerical value of expression
|
| @ variable[n]=expression
| set variable element n to numerical value of expression
|
|
