String length of bash

Question

I have written this to find the length of the string, but it doesn't show the length of the string.

Is there something wrong with what I have written? I'm just a beginner in bash.

Str=abcdefghj

echo "Str is:" `expr length $Str` "characters long"

There's nothing wrong with what you've written, but it is likely that the implementation of `expr` that you are using does not support the `length` argument. From the standard for `expr`: "The use of string arguments length, substr, index, or match produces unspecified results." — William Pursell, Oct 05 '17 at 18:47
If your shell is Bash, there should basically never be any reason to use `expr`. It is necessary and useful in `sh` which has much more limited shell builtin facilities for arithmetic and string manipulation. — tripleee, Oct 02 '21 at 08:37

score 28 · Answer 1 · answered Jul 19 '13 at 16:23

28

This can be done natively in bash, no need to resort to expr

echo ${#Str}

answered Jul 19 '13 at 16:23

iruvar

1

`${#Str}` counts characters based on local, same as `echo -n $Str | wc -m`. To get the size in bytes set the local to C, `LC_ALL=C echo ${#Str}` – Phernost Aug 27 '18 at 16:02

score 2 · Answer 2 · answered Oct 05 '17 at 18:27

2

Here is couple of ways to calculate length of variable :

echo ${#Str}
echo -n $Str | wc -m
echo -n $Str | wc -c
printf $Str | wc -m
expr length $Str
expr $Str : '.*'

answered Oct 05 '17 at 18:27

Mukesh Shakya

All except the first use external processes, which generally you want to avoid whenever you can. The alternatives might be useful for `sh` scripts (see also [Difference between sh and bash](https://stackoverflow.com/questions/5725296/difference-between-sh-and-bash)). – tripleee Oct 02 '21 at 08:54

score -2 · Answer 3 · edited Oct 02 '21 at 08:43

-2

Try something like this:

echo "Str is: `expr length $Str` characters long"

edited Oct 02 '21 at 08:43

tripleee

answered Nov 23 '18 at 22:45

Angel García

2

Can you explain why you believe this answers the OP's question? Have _you_ tried both ways and compared the results? – GoojajiGreg Nov 24 '18 at 02:17
The downvotes and the preceding comment are probably (at least partially) due to Markdown formatting errors which originally wrecked this answer. Still, probably prefer modern `$(command substitution)` syntax over the legacy backticks from the early 1990s, and maybe actually don't recommend `expr`. Oh, and [absolutely quote the string variable.](https://stackoverflow.com/questions/10067266/when-to-wrap-quotes-around-a-shell-variable) Anyway, this isn't really an improvement over the OP's code. – tripleee Oct 02 '21 at 08:53

3 Answers3