|
Size: 830
Comment: what if $varname == "length" :-(
|
Size: 1280
Comment:
|
| Deletions are marked like this. | Additions are marked like this. |
| Line 3: | Line 3: |
| The fastest way, not requiring external programs (but usable only with [[BASH]] and KornShell): | The fastest way, not requiring external programs (but not usable in Bourne shells): |
| Line 6: | Line 6: |
| # POSIX | |
| Line 12: | Line 13: |
| # Bourne | |
| Line 20: | Line 22: |
| # Bourne, with GNU expr(1) | |
| Line 25: | Line 28: |
| This second version is not specified in [[POSIX]], so is not portable across all platforms. | This second version is not specified in [[POSIX]], so is not portable across all platforms. However, if {{{$varname}}} expands to {{{"length"}}}, the first version will fail with BSD/GNU {{{expr}}}. |
| Line 27: | Line 30: |
| However, if {{{$varname}}} expands to {{{"length"}}}, the first version will fail with BSD/GNU {{{expr}}}. | A portable way is: |
| Line 30: | Line 33: |
| 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 |
|
| Line 33: | Line 59: |
| Returns the Number of Elements in an Array. | Returns the number of elements in an array. |
| Line 36: | Line 62: |
| # Korn/Bash | |
| Line 39: | Line 66: |
| Returns the length of the Arrays Element i. | Returns 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
${#varname}or for Bourne shells:
# Bourne expr "$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.