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| [[Anchor(faq7)]] | <<Anchor(faq7)>> |
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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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| ${#varname} | # POSIX "${#varname}" |
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| or | (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: |
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| expr "$varname" : '.*' | # Bourne expr "x$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 `$varname` values that are `expr` operators) |
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| or | or: |
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| expr length "$varname" | # Bourne, with GNU expr(1) expr length "x$varname" - 1 |
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| (for a BSD/GNU version of {{{expr}}}. Do not use this, because it is not ["POSIX"]). | (BSD/GNU {{{expr}}} only) This second version is not specified in [[POSIX]], so is not portable across all platforms. One may also use `awk`: {{{ # Bourne with POSIX awk awk 'BEGIN {print length(ARGV[1])}' "$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. ---- 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
"${#varname}"(note that with bash 3 and above, that's the number of characters, not bytes, which is a significant differences in multi-byte locales. Behaviour of other shells in that regard vary).
or for Bourne shells:
# Bourne expr "x$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.