getting file size from the ls output

Question

I have a variable named $lsoutput in which I store the result of the ls -l command
It's content is

-rw-r--r-- 1 root ftp 44 Apr 29 2003 first_file.txt
I would like to get the size of that file.
I useed the following regular expression

if [[ "$lsoutput" =~ ^[-rwx]{10}[[:space:]][[:digit:]]+[[:space:]][[:alnum:]]+[[:space:]][[:alnum:]]+[[:space]]([[:digit:]]+) ]]
    echo ${BASH_REMATCH[1]}
fi

Unfortuantely this regexp does not work. What is wrong with it? Can you provide a correct one? Thanks for your help

See [Why you shouldn't parse the output of `ls`](http://mywiki.wooledge.org/ParsingLs) -- particularly the section titled "Getting Metadata From A File" — Charles Duffy, May 31 '17 at 15:28
Related: [Portable way to get file size in bytes in shell](https://stackoverflow.com/questions/1815329/portable-way-to-get-file-size-in-bytes-in-shell) — Charles Duffy, May 31 '17 at 15:34
(To be clear, I didn't add the above "related" link to the duplicate list because the primary duplicate asks about the `ls` approach *in the question itself*, and has [at least one answer](https://stackoverflow.com/a/25466100/14122) describing how to use `ls` for the purpose in a way that avoids some of the more common failure modes). — Charles Duffy, May 31 '17 at 15:45

Bas van Dijk · Answer 1 · 2017-05-31T15:23:50.980

1

Isn't it easier to use:

ls -l | awk '{print $5}'

Which just prints the file size?

edited May 31 '17 at 15:23

answered May 31 '17 at 15:11

Bas van Dijk

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Missing closing apostrophe, also the `-rt` options are not necessary for this to work. Anyway much cleaner than using that long regexp here, specially if it is wrong. – Ho Zong May 31 '17 at 15:20
SO does not let me edit the answer as it needs at least 6 chars to edit, and did not want to just make some rewording, this is your answer... so please edit it. – Ho Zong May 31 '17 at 15:21
Fixed with your comment, thanks! – Bas van Dijk May 31 '17 at 15:24

score 1 · Answer 2 · answered May 31 '17 at 15:15

1

There's much easier way.

stat --format=%s <FILE>

The above command prints the size of the file in bytes.

Parsing ls output is not recommended.

answered May 31 '17 at 15:15

Arkadiusz Drabczyk

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One can also use GNU find: `find "$file" -maxdepth 0 -printf '%s\n'`, for instance. – Charles Duffy May 31 '17 at 15:31
Or `stat -f %z ` on MacOS – Molomby Mar 29 '20 at 04:19

score 0 · Answer 3 · answered May 31 '17 at 15:26

0

with cut:

ls -l|tr -s ' ' |cut -d' ' -f5

answered May 31 '17 at 15:26

tso

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getting file size from the ls output

3 Answers3