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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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Though that one will fail for values of $varname that contain backslash characters, so you may prefer:

{{{
# Bourne with POSIX awk
awk 'BEGIN {print length(ARGV[1]);exit}' "$varname"
}}}

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)}'

Though that one will fail for values of $varname that contain backslash characters, so you may prefer:

# Bourne with POSIX awk
awk  'BEGIN {print length(ARGV[1]);exit}' "$varname"


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)