Differences between revisions 12 and 16 (spanning 4 versions)
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Comment:
← Revision 16 as of 2015-03-05 00:24:26 → ⇥
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Editor: izabera
Comment: syntax hl
Deletions are marked like this. Additions are marked like this.
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{{{ {{{#!highlight bash
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${#varname} "${#varname}"
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{{{ {{{#!highlight bash
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expr "$varname" : '.*' expr "x$varname" : '.*' - 1
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({{{expr}}} prints the number of characters or bytes matching the pattern {{{.*}}}, which is the length of the string (in bytes for GNU `expr`).) ({{{expr}}} prints the number of characters or bytes matching the pattern {{{.*}}}, which is the length of the string (in bytes for GNU `expr`). The `x` is necessary to avoid problems with `$varname` values that are `expr` operators)
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{{{ {{{#!highlight bash
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expr length "$varname" expr length "x$varname" - 1
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This second version is not specified in [[POSIX]], so is not portable across all platforms.  However, if {{{$varname}}} expands to any `expr` operator like `+` or `(` or `length`, the first version will fail.

A portable way is:

{{{
expr \( "X$varname" : ".*" \) - 1
}}}		 This second version is not specified in [[POSIX]], so is not portable across all platforms.
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{{{
# Bourne
awk -v x="$varname" 'BEGIN {print length(x)}'
}}}

Though that one will fail for values of $varname that contain backslash characters, so you may prefer:

{{{		 {{{#!highlight bash
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awk 'BEGIN {print length(ARGV[1]);exit}' "$varname" awk 'BEGIN {print length(ARGV[1])}' "$varname"
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{{{ {{{#!highlight bash
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${#arrayname[@]} "${#arrayname[@]}"
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Returns the number of elements in an array. Expands to the number of elements in an array.
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{{{ {{{#!highlight bash
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${#arrayname[i]} "${#arrayname[i]}"
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Returns the length of the array's element i. Expands to the length of the array's element i.

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

The fastest way, not requiring external programs (but not usable in Bourne shells): 

   1 # POSIX
   2 "${#varname}"

(note that with bash 3 and above, that's the number of characters, not bytes, which is a significant differences in multi-byte locales. Behaviour of other shells in that regard vary).

or for Bourne shells: 

   1 # Bourne
   2 expr "x$varname" : '.*' - 1

(expr prints the number of characters or bytes matching the pattern .*, which is the length of the string (in bytes for GNU expr). The x is necessary to avoid problems with $varname values that are expr operators)

or: 

   1 # Bourne, with GNU expr(1)
   2 expr length "x$varname" - 1

(BSD/GNU expr only)

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

One may also use awk: 

   1 # Bourne with POSIX awk
   2 awk  'BEGIN {print length(ARGV[1])}' "$varname"

(there, whether the length is expressed in bytes or characters depends on the implementation (for instance, it's characters for GNU awk, but bytes for mawk).

Similar needs: 

   1 # Korn/Bash
   2 "${#arrayname[@]}"

Expands to the number of elements in an array. 

   1 # Korn/Bash
   2 "${#arrayname[i]}"

Expands to the length of the array's element i.

CategoryShell

BashFAQ/007 (last edited 2015-03-05 00:24:26 by izabera)