Command Reference Guide

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STANDARD Printed by: Nora Chuang [nchuang] STANDARD

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ksh(1) ksh(1)

of all subscripts must be in the range of 0 through 1023. Arrays need not be declared. Any reference to a

named parameter with a valid subscript is legal and an array is created if necessary. Referencing an array

without a subscript is equivalent to referencing the ﬁrst element.

The value of a named parameter can also be assigned by writing:

name=value [name=value ] ...

If the -i integer attribute is set for name, the value is subject to arithmetic evaluation as described below.

Positional parameters, parameters denoted by a number, can be assigned values with the set special com-

mand. Parameter $0 is set from argument zero when the shell is invoked.

The character $ is used to introduce substitutable parameters.

${parameter} Substitute the value of the parameter, if any. Braces are required when param-

eter is followed by a letter, digit, or underscore that should not be interpreted as

part of its name or when a named parameter is subscripted. If parameter is one

or more digits, it is a positional parameter. A positionalparameter of more than

one digit must be enclosed in braces. If parameter is * or @ all the positional

parameters, starting with $1, are substituted (separated by a ﬁeld separator

character). If an array identiﬁer with subscript

* or @ is used, the value for

each element is substituted (separated by a ﬁeld separator character). The shell

reads all the characters from

${ to the matching } as part of the same word

even if it contains braces or metacharacters.

${#parameter} If parameter is * or @, the number of positional parameters is substituted.

Otherwise, the length of the value of the parameter is substituted.

${#identifier[*]} Substitute the number of elements in the array identiﬁer.

${parameter:-word}

If parameter is set and is non-null, substitute its value; otherwise substitute

word.

${parameter:=word}

If parameter is not set or is null, set it to word; then substitute the value of the

parameter. Positional parameters cannot be assigned in this way.

${parameter:?word}

If parameter is set and is non-null, substitute its value; otherwise, print word

and exit from the shell. If word is omitted, a standard message is printed.

${parameter:+word}

If parameter is set and is non-null, substitute word; otherwise substitute noth-

ing.

${parameter#pattern}

parameter##pattern}

If the shell pattern matches the beginning of the value of parameter, the value of

this substitution is the value of the parameter with the matched portion deleted;

otherwise the value of this parameter substituted. In the former case, the smal-

lest matching pattern is deleted; in the latter case, the largest matching pattern

is deleted.

${parameter%pattern}

parameter%%pattern}

If the shell pattern matches the end of the value of parameter, the value of

parameter with the matched part is deleted; otherwise substitute the value of

parameter. In the former, the smallest matching pattern is deleted; in the

latter, the largest matching pattern is deleted.

In the above, word is not evaluated unless it is used as the substituted string. Thus, in the following

example, pwd is executed only if d is not set or is null:

echo ${d:-$(pwd)}

If the colon (:) is omitted from the above expressions, the shell only checks to determine whether or

not parameter is set.

HP-UX Release 11i: December 2000 − 4 − Section 1−−399

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