Variable Substitution

${ variable }

value of variable

${# variable }

length of variable

${ variable : ?/span> word }

value of variable if set and not null, else print word . If : is omitted, variable is only checked if it is set.

${ variable := word }

value of variable if set and not null, else variable is set to word , then expanded. If : is omitted, variable is only checked if it is set.

${ variable :?}

value of variable if set and not null, else print " variable: parameter null or not set ". If : is omitted, variable is only checked if it is set.

${ variable :? word }

value of variable if set and not null, else print value of word and exit. If : is omitted, variable is only checked if it is set.

${ variable :+ word }

value of word if variable is set and not null, else nothing is substituted. If : is omitted, variable is only checked if it is set.

${ variable # pattern }

value of variable without the smallest beginning portion that matches pattern

${ variable ## pattern }

value of variable without the largest beginning portion that matches pattern

${ variable % pattern }

value of variable without the smallest ending portion that matches pattern

${ variable %% pattern }

value of variable without the largest ending portion that matches pattern

$ #

number of positional parameters

$ @

all positional parameters (" $1 ", " $2 ", ..., " $ n ")

$ *

all positional parameters (" $1 $2 ... $ n ")

$ ?

exit status of the last command

$$

process id of the current shell

$ ?/span>

current options in effect

$ !

process id of last background command

CDPATH

search path for cd when not given a full pathname (no default)

COLUMNS

window width for in-line edit mode and select command lists (default 80 )

EDITOR

pathname of the editor for in-line editing (default /bin/ ed )

ENV

pathname of the environment file (no default)

FCEDIT

default editor for the fc command

FPATH

search path for auto-loaded functions pathname of the history file

HISTFILE

pathname of the history file (default $HOME/ .sh_history )

HISTSIZE

number of commands to save in history file (default 128 )

HOME

home directory

IFS

internal field separator (default space, tab, newline)

LINES

specifies column length for select lists

MAIL

name of mail file

MAILCHECK

specifies how often to check for mail (default 600 seconds)

MAILPATH

search path for mail files (no default)

OLDPWD

previous working directory

OPTARG

value of the last getopts option argument

OPTIND

index of the last getopts option argument

PATH

search path for commands (default /bin:/usr/bin: )

PPID

process id of the parent shell

PS1

primary prompt string (default $, #)

PS2

secondary prompt string (default >)

PS3

select command prompt (default #?)

PS4

debug prompt string (default +)

RANDOM

contains a random number

REPLY

contains input to read command when no variables given

SECONDS

contains number of seconds since Korn shell invocation

SHELL

pathname of shell

TERM

specifies your terminal type (no default)

TMOUT

Korn shell timeout variable (default )

VISUAL

pathname of the editor for in-line editing