Diff for "BashFAQ/007"

Differences between revisions 2 and 6 (spanning 4 versions)

Is there a function to return the length of a string?

The fastest way, not requiring external programs (but usable only with BASH and KornShell):

${#varname}

or for Bourne shells:

expr "$varname" : '.*'

(expr prints the number of characters matching the pattern .*, which is the length of the string.)

or:

expr length "$varname"

(BSD/GNU expr only)

This second version is not specified in POSIX, so is not portable across all platforms.

However, if $varname expands to "length", the first version will fail with BSD/GNU expr.

${#arrayname[@]}

Returns the Number of Elements in an Array.

${#arrayname[i]}

Returns the length of the Arrays Element i.

-  ⇤ ← Revision 2 as of 2008-11-22 14:08:37 → 
  Size: 484
  Editor: localhost
  Comment: converted to 1.6 markup
+   ← Revision 6 as of 2011-02-28 22:27:41 → ⇥
  Size: 830
  Editor: 203-214-41-227
  Comment: what if $varname == "length" :-(
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-or
+or for Bourne shells:
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-({{{expr}}} prints the number of characters matching the pattern {{{.*}}}, which is the length of the string)
+({{{expr}}} prints the number of characters matching the pattern {{{.*}}}, which is the length of the string.)
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-or
+or:
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-(for a BSD/GNU version of {{{expr}}}. Do not use this, because it is not [[POSIX]]).
+(BSD/GNU {{{expr}}} only)

This second version is not specified in [[POSIX]], so is not portable across all platforms.

However, if {{{$varname}}} expands to {{{"length"}}}, the first version will fail with BSD/GNU {{{expr}}}.

{{{
${#arrayname[@]}
}}}

Returns the Number of Elements in an Array.

{{{
${#arrayname[i]}
}}}

Returns the length of the Arrays Element i.

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CategoryShell