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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
"
${#varname}"
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(note that with `bash` 3 and above, that's the number of characters, not bytes, which is a significant differences in multi-byte locales. Behaviour of other shells in that regard vary).
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expr "$varname" : '.*' # 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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Another one: or:
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expr length "$varname" # Bourne, with GNU expr(1)
expr length "x$varname" - 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.

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.


CategoryShell

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