Is there a function to return the length of a string?

The fastest way, not requiring external programs (but not usable in Bourne shells):

   1 # POSIX
   2 "${#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:

   1 # Bourne
   2 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:

   1 # Bourne, with GNU expr(1)
   2 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:

   1 # Bourne with POSIX awk
   2 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:

   1 # Korn/Bash
   2 "${#arrayname[@]}"

Expands to the number of elements in an array.

   1 # Korn/Bash
   2 "${#arrayname[i]}"

Expands to the length of the array's element i.

CategoryShell