10.3.2 isEmptyVar (evaluates to a null variable)

Syntax

isEmptyVar  variable-name

Description

This command evaluates whether a value of variable is substituted for variable.

If either of the following conditions is met, 1 is output:

• Variable is not defined

• A variable is not substituted in variable

• A blank character string is substituted in variable

This command outputs 0.

• A variable with not less than one character is substituted in variable

Arguments

variable-name

This command specifies a variable name to be determined.

If you specify the array, specify the array including element number (example: array[1]).

Output to the standard output

1 or 0.

Return codes

Notes

• Do not specify a variable name starting with "adsh" for the variable-name argument. If you specify such a variable name, it might conflict with the name of another variable used within the part and produce invalid output.

• The character string that can be specified for variable-name is the same as character string that can be used as variable name. However, whether the character string can be specified is not verified.

Examples

typeset var1
isEmptyVar var1    # "1" is output.
var1=""
isEmptyVar var1    # "1" is output.
var1=100
isEmptyVar var1    # "0" is output.

#If variable var1 is null, return 1.
result=$(isEmptyVar var1)
if [[ $result -eq 1 ]]; then
  return 1
fi