Korn Shell Variables

Variables are set with the = operator as in Bourne shell. No space is allowed around the = operator. Variables may have attributes assigned by typeset with the following syntax:

Any variable can be assigned the output of a command or of a file with the syntax:

Variables are removed by the unset builtin. To define a variable that executes a script file using Ksh syntax, do the following:

> ksh
$ cv=$(<kls)
$ echo $cv
ls -al
$
$ $cv
total 5
drwxr-xr-x   3 john     users       8192 Mar 10 10:48 .
drwxr-x--x  17 john     users       8192 Mar  9 16:05 ..
-rw-r--r--   1 john     users        299 Mar  9 11:25 a.a
-rwxr-xr-x   1 john     users        261 Mar 10 08:44 cread
-rw-r--r--   1 john     users         37 Jun 18  1998 er

_ ** ** ** Ksh** _ ** Special variables are:**

__ Korn Shell Special Variables

# | number of positional parameters ? | exit status $ | process ID - (dash) | current options _ (underscore) | the last argument of the previous command ! | process ID of last background ERRNO | error no. of last failed system call LINENO | the line no. of the current script line in execution OLDPWD | previous cd directory OPTARG | last option processed by getopts OPTIND | index of last option processed by getopts PPID | parent PID PWD | current directory RANDOM | random funcion REPLY | menu item no. in response to select Ksh command SECONDS | seconds since shell invocation CDPATH | search path for cd command COLUMNS | edit window width EDITOR | editor management ENV | generate path name in tracked alias and functions FCEDIT | default editor for history processing command fc FPATH | search path for functions IFS | internal field separator HISTFILE | store command history file HISTSIZE | history buffer size HOME | home directory LANG | system locale LC_COLLATE | collating sequence LC_CTYPE | character classification LC_MESSAGES | language for system messages LC_MONETARY | monetary format LC_NUMERIC | numeric format LC_TIME | date and time format LINES | column length LOGNAME | login name MAIL | mail notify MAILCHECK | mail notify interval MAILPATH | mail notify NLSPATH | search path for messages PATH | searc path for commands PS1 | primary promt PS2 | secondary prompt PS3 | selection prompt (default #?) PS4 | trace prompt (default +) SHELL | shell in use TMOUT | command timeout to terminate shell VISUAL | editor option _ ** _**

** Variables are protected by braces:**

__

$ print Current options/ERRNO: ${-}, $ERRNO
Current options/ERRNO: ism, 10

_ ** _Metacharacters are printed when prefixed by\. **

__ Korn Shell Variable Usage and Setting Rules

varlen=${#var} | variable length var=${var1:-value} | var=var1 if var1 set, var=value if var1.not.set or empty var=${var1-value} | var=var1 if var1 set, var=value only if var1.not.set var=${var1:=var2} | var=$var1 if var1 set and not empty, else = $var2 var=${var1=var2} | var=$var1 if var1 set even if empty, else = $var2 var=${var1:+var2} | var=$var2 if var1 set and not empty, else var not set var=${var1:+var2} | var=$var2 if var1 set even if empty, else var not set var=${var1#var2} | var=var1 with smallest part of left matched var2 deleted var=${var1##var2} | var=var1 with largest part of left matched var2 deleted var=${var1%var2} | var=var1 with smallest part of right matched var2 deleted var=${var1%%var2} | var=var1 with largest part of right matched var2 deleted var=${var1:?} | var=var1 if var1 set else error message var=${var1:?var2} | var=var1 if var1 set else var=var2 and exit _ ** _**

Korn shell can handle arrays as ** C** _ ** shell but with a different syntax.**_

__ Korn Shell Array Syntax

arr[0]=val0 arr[1]=val1 ... | init array in any order set -A arr val0 val1 ... | alternate init for ordered array typeset arr[0]=val0 arr[1]=val1 ... | alternate init array in any order ${arr}, $arr | array element zero ${arr[n]} | array element n ${arr[n+2] | array element n+2 ${arr[$i]} | array element $i ${arr[*]}, ${arr[@]} | all elements of array ${#arr[*]}, ${#arr[@]} | number of array elements ${#arr[n]} | length of array element n _ ** _**

** Example of array usage:**

__

#!/bin/ksh
#-----------karray: arrays with Korn shell
#
echo Proc $0: arrays in Korn shell
echo
set -A rgb red green blue yellow magenta cyan
print rgb is a ${#rgb[*]} items color array with values:
print ${rgb[*]}
print 4-th item is ${rgb[1+3]} ${#rgb[4]}-bytes long
#
#----------end script------------------

_ ** The_ ** set +A _ ** statement allows partial redefinition of ordered array elements. Consider the following:**_

$ set -A rgb red green blue yellow magenta cyan
$ print ${rgb[*]}
red green blue yellow magenta cyan

If you use ** -A** _ ** to change only the first item of array_ ** rgb _ ** _, the array is truncated. If you use__ ** +A _ ** , the first items are changed keeping the remaining ones:**_

$ set -A rgb red green blue
$ print ${rgb[*]}
red green blue
$ set -A rgb red green blue yellow magenta cyan
$ set +A rgb rosso
$ print ${rgb[*]}
rosso green blue yellow magenta cyan

__

In Korn shell quotes have the same usage as in Bourne shell.

__

_single quotes_ '` hide meaning of special characters, do not perform variable substitution within quoted string

double quotes " preserve embedded spaces and newlines, set vars to

NULL , display single quotes, perform variable substitution back quotes ``` assign command output to vars `