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Variable/Attribute Assignment Format
| variable=
| declare variable and set it to null
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| typeset variable=
| declare variable and set it to null. If used within a function, then a local variable is declared.
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| variable=value
| assign value to variable
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| typeset variable=value
| assign value to variable. If used within a function, then a local variable is declared.
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| typeset –attribute variable=value
| assign attribute and value to variable
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| typeset –attribute variable
| assign attribute to variable
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| typeset +attribute variable
| remove attribute from variable (except readonly)
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Variable/Attribute Listing Format
| typeset –attribute
| display a list of variable names and their values that have attribute set
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| typeset +attribute
| display a list of variable names that have attribute set
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VARIABLE ATTRIBUTES
Variables can have one or more attributes that specify their internal representation, scope, or the way they are displayed.
Variable Attribute Assignment Format
| typeset –H variable
| Set UNIX to host-name file mapping for non-UNIX systems
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| typeset –i variable
| Set variable to be integer type
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| typeset –in variable
| Set variable to be integer type with base n
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| typeset –l variable
| Set variable to lower case
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| typeset –L variable
| Left justify variable; the field width is specified by the first assignment
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| typeset –Ln variable
| Left justify variable; set field width to n
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| typeset –LZn variable
| Left justify variable; set field width to n and strip leading zeros
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| typeset –r variable
| Set variable to be readonly (same as readonly)
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| typeset –R variable
| Right justify variable; the field width is specified by the first assignment
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| typeset –Rn variable
| Right justify variable; set field width to n
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| typeset –RZn variable
| Right justify variable; set field width to n and fill with leading zeros
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| typeset –t variable
| Set the user-defined attribute for variable. This has no meaning to the Korn shell.
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| typeset –u variable
| Set variable to upper case
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| typeset –x variable
| Automatically export variable to the environment (same as export)
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| typeset –Z variable
| Same as typeset –RZ
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VARIABLE SUBSTITUTION
Variable values can be accessed and manipulated using variable expansion. Basic expansion is done by preceding the variable name with the $ character. Other types of expansion can be used to return portions or the length of variables, use default or alternate values, assign default or alternate values, and more.
Variable Expansion Format
| ${variable}
| value of variable
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| ${#variable}
| length of variable
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| ${variable:–word}
| value of variable if set and not null, else print word. If : is omitted, variable is only checked if it is set.
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| ${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.
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| ${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.
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| ${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.
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| ${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.
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| ${variable#pattern}
| value of variable without the smallest beginning portion that matches pattern
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| ${variable##pattern}
| value of variable without the largest beginning portion that matches pattern
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| ${variable%pattern}
| value of variable without the smallest ending portion that matches pattern
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| ${variable%%pattern}
| value of variable without the largest ending portion that matches pattern
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SPECIAL PARAMETERS
Some special parameters are automatically set by the Korn shell, and usually cannot be directly set or modified.
Special Parameters
| $#
| number of positional parameters
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| $@
| all positional parameters ("$1", "$2", ..., "$n")
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| $*
| all positional parameters ("$1 $2 ... $n")
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| $?
| exit status of the last command
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| $$
| process id of the current shell
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| $–
| current options in effect
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| $!
| process id of the last background command or co-process
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