Differences between revisions 6 and 7
Revision 6 as of 2011-02-28 22:27:41
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Editor: 203-214-41-227
Comment: what if $varname == "length" :-(
Revision 7 as of 2011-03-01 00:03:52
Size: 1014
Editor: GreyCat
Comment: Mark which version works where; add awk version; cosmetics
Deletions are marked like this. Additions are marked like this.
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The fastest way, not requiring external programs (but usable only with [[BASH]] and KornShell): The fastest way, not requiring external programs (but not usable in Bourne shells):
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# POSIX
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# Bourne
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# Bourne, with GNU expr(1)
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This second version is not specified in [[POSIX]], so is not portable across all platforms. This second version is not specified in [[POSIX]], so is not portable across all platforms.  However, if {{{$varname}}} expands to {{{"length"}}}, the first version will fail with BSD/GNU {{{expr}}}.
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However, if {{{$varname}}} expands to {{{"length"}}}, the first version will fail with BSD/GNU {{{expr}}}. One may also use `awk`:
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# Bourne
awk -v x="$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.

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.

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)