mjhjmtu

I have the following script which counts characters in user input:

 echo -n "Type text: ";
 read mystring;
 echo -n $mystring | wc -m;

Without the "-n" in the last line, the character count would be wrong because it would also include the newline character put there by echo (so the count for e.g. "abc" would be 4 instead of 3.)

For the sake of practice I now want to do this correction in a more complicated way. The general idea is like this:

 var=$($mystring | wc -m);
 echo -n "Type text: ";
 read mystring;
 echo $(( $var - 1 ));

So the character count of user input becomes $var and then I subtract 1 from $var. How do I make it work?

Your script does not work for several reasons:

• You start by initializing var to be equal to the output of running the command | wc -m because mystring is at this point null.


• Even if it were not null, it would attempt to run its contents as a command, and send that output into wc.

You have to A> do things in the right order, and ii.> do the correct things:

read -p "Type something > " mystring
var="$( wc -m <<< "$foo" )"
echo $(($var-1))

If you want to count the number of characters in what the user entered up to but not including the newline character, then it should be:

#! /bin/sh -
printf 'Type text: '
IFS= read -r userInput
length=$(printf %s "$userInput" | wc -m)
# or:
length=$#userInput

If you want to include the newline character that the user possibly entered, then:

#! /bin/sh -
printf 'Type text: '
IFS= read -r userInput && userInput="$userInput
"
length=$(printf %s "$userInput" | wc -m)
# or:
length=$#userInput

read will typically return true if a full line was input (the newline character is present) which is why we append one if read was successful.

Note that in most shell implementations (zsh being the exception), it won't work properly if the user enters a NUL (aka ^@) character.

To work around that, you could do:

printf 'Type text: '
length=$(line | wc -m)

instead. Or:

length=$(line | tr -d 'n' | wc -m)
# or
length=$(($(line | wc -m) - 1)) # as line always includes a newline on
 # output even if one was not provided on
 # input.

if you don't want to count the newline.

The behaviour will vary as well if the user manages to enter bytes that don't form part of valid characters. You'll also find some sh implementations whose $#var doesn't work properly with multi-byte characters (would return the length in bytes instead of characters).

expr " $mystring" : '.*' - 1

will return the length of the contents of the shell variable mystring

In bash you'd use

#!/usr/bin/env bash

read -p 'Type text: ' userInput
printf 'Your input was %d chars longn' "$#userInput"

The string count can be retrieved by $#var. Using wc is in this case unnecessary