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Size: 1083
Comment: portable (but ugly) expr method suggested in FreeBSD expr page to avoid case where "$varname"=length and using GNU expr :-/
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| ${#varname} | "${#varname}" |
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(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). |
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| expr "$varname" : '.*' | expr "x$varname" : '.*' - 1 |
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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 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 `$varname` values that are `expr` operators) |
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| expr length "$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 {{{"length"}}}, the first version will fail with BSD/GNU {{{expr}}}. 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="$varname" 'BEGIN {print length(x)}' |
# Bourne with POSIX awk awk 'BEGIN {print length(ARGV[1])}' "$varname" |
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| (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`). | |
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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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| ${#arrayname[i]} | "${#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):
# POSIX
"${#varname}"(note that with bash 3 and above, that's the number of characters, not bytes, which is a significant differences in multi-byte locales. Behaviour of other shells in that regard vary).
or for Bourne shells:
# Bourne expr "x$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 $varname values that are expr operators)
or:
# Bourne, with GNU expr(1) expr length "x$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:
# Bourne with POSIX awk
awk 'BEGIN {print length(ARGV[1])}' "$varname"(there, whether the length is expressed in bytes or characters depends on the implementation (for instance, it's characters for GNU awk, but bytes for mawk).
Similar needs:
# Korn/Bash
"${#arrayname[@]}"Expands to the number of elements in an array.
# Korn/Bash
"${#arrayname[i]}"Expands to the length of the array's element i.