korn shell test null string

So [ -z "$1" ] is a proper way of testing if $1 is empty, and [ &...

So [ -z "$1" ] is a proper way of testing if $1 is empty, and [ "$x" = "$y" ] is a proper presumably when "interesting" strings like "-o a=a" are tested. This method works for the traditional bourne shell, as well as ksh, and bash.

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empty is a string without char but defined, so in this case [ -z "${My...

empty is a string without char but defined, so in this case [ -z "${MyVar}" ]. null is the Use the test -n option, or the ksh / bash [[ ]] equivalent.

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One way to test for (non-)empty string is to use test and -z (-n) Your shel...

One way to test for (non-)empty string is to use test and -z (-n) Your shell (here ksh on AIX) starts having errors as soon as your subshell (here.

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hi all, i have a shell (ksh) script where i am reading line by line from a ...

hi all, i have a shell (ksh) script where i am reading line by line from a grep to check if the grep command actually returned something or was null. i can do -z, or even just the unquoted string alone within test brackets (see  How to check if two variable are empty strings at once.

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The simplest expression is a string which is true if the string is non-empt...

The simplest expression is a string which is true if the string is non-empty is not set, test, [, and [[ behave as in the standard Korn Shell and quietly ignore any.

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Matching Patterns; Conditional Statements; Test Objects (Files, Directories...

Matching Patterns; Conditional Statements; Test Objects (Files, Directories, etc.) _str2_ ]] strings not equal [[ _str1_ _str2_ ]] _pattern_ ]] str1!= pattern [[ -z _str_ ]] str is null [[ -n _str_ ]] str is not null [ x=y.

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Return true if a bash variable is unset or set to the empty string: if [ -z...

Return true if a bash variable is unset or set to the empty string: if [ -z .. Bash Shell: Find Out If a Variable Is Set or Not; bash(1); test(1); help [; help [[ Double brackets were introduced by David Korn in ksh in the early 80s.

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Check if parameter is NULL (shell scripting) Programming & Packaging. I...

Check if parameter is NULL (shell scripting) Programming & Packaging. I'd like it to work under ksh, but if it can only be done under bash then fine!:) the quoted test strings then echo "Strings \"$1\" and \"$2\" are not null.

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Test Operators These are the operators that are used with the [[. Selection...

Test Operators These are the operators that are used with the [[. Selection from Learning the Korn Shell, 2nd Edition [Book] -n string, string is non-null.

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Ensure that variables exist (i.e., are defined and have non-null values) Th...

Ensure that variables exist (i.e., are defined and have non-null values) The first group of string-handling operators tests for the existence of variables . Advanced Unix users will find the Korn shell's regular expression capabilities useful for.

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This will return true if a variable is unset or set to the empty string (&q...

This will return true if a variable is unset or set to the empty string (""). You can simplify the test for a variable that does contain a value to: if [[ $variable ]]. This syntax is compatible with ksh (at least ksh93, anyway). It does not.

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To make a ksh script (which is a ksh program) crate a new file with a start...

To make a ksh script (which is a ksh program) crate a new file with a starting line like: A script has four types of lines: The shell defining line at the top, empty lines, have a name which is identical to a unix command: So the script must NOT be called "test"! There is no difference between strings and numbers: price=

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A tutorial on Unix shell scripting with Bourne and Korn shells. shells for ...

A tutorial on Unix shell scripting with Bourne and Korn shells. shells for which [ is an external program, the only way to test for a null string is.

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test "$X" = abc && print "X is set to abc" or [...

test "$X" = abc && print "X is set to abc" or [ "$X" = abc ] && print "X is set to is set to null" Checking Patterns The Korn shell also lets you compare strings to.

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Try using the -z test: if [ -z "$1" ] && [ -z "$2&qu...

Try using the -z test: if [ -z "$1" ] && [ -z "$2" ]. From man bash: z string True if the length of string is zero.

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