Differences between revisions 4 and 8 (spanning 4 versions)
Revision 4 as of 2009-06-09 13:19:16
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Editor: localhost
Comment: its about length.. it should also bring examples for arrays
Revision 8 as of 2011-03-04 23:01:36
Size: 1083
Editor: 203-214-41-227
Comment: portable (but ugly) expr method suggested in FreeBSD expr page to avoid case where "$varname"=length and using GNU expr :-/
Deletions are marked like this. Additions are marked like this.
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The fastest way, not requiring external programs (but usable only with [[BASH]] and KornShell): The fastest way, not requiring external programs (but not usable in Bourne shells):
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# POSIX
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# Bourne
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Another one: or:
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# Bourne, with GNU expr(1)
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(This is 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}}}.

A portable way is:
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expr \( "X$varname" : ".*" \) - 1
}}}

One may also use `awk`:

{{{
# Bourne
awk -v x="$varname" 'BEGIN {print length(x)}'
}}}

------

Similar needs:

{{{
# Korn/Bash
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Returns the Number of Elements in an Array. Returns the number of elements in an array.
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# Korn/Bash
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Returns the length of the Arrays Element i. Returns the length of the array's element i.

----
CategoryShell

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

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

# POSIX
${#varname}

or for Bourne shells:

# Bourne
expr "$varname" : '.*'

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

or:

# Bourne, with GNU expr(1)
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.

A portable way is:

expr \( "X$varname" : ".*" \) - 1

One may also use awk:

# Bourne
awk -v x="$varname" 'BEGIN {print length(x)}'


Similar needs:

# Korn/Bash
${#arrayname[@]}

Returns the number of elements in an array.

# Korn/Bash
${#arrayname[i]}

Returns the length of the array's element i.


CategoryShell

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