Linux - Check if a file has multiple lines

Question

Is there a command or bash function to check if a file has multiple lines? Lets say i have these two files:

foo.txt

Hello World

bar.txt

Hello
World

You can use `wc -l` to count the number of lines in a file. – dreamlax Jan 25 '16 at 08:38 — dreamlax, Jan 25 '16 at 08:38

score 1 · Answer 1 · answered Jan 25 '16 at 08:52

1

You can use this script:

name:test.sh

#!/bin/bash

back=`wc -l $1`
nl=${back:0:1}

if [ $nl = "1" ];then
    echo "single line"
else
    echo "multi lines"
fi

use this command to change the file mod:

chmod a+x test.sh

Then execute the script,paramater is the file you want to test:

./test.sh hello

answered Jan 25 '16 at 08:52

hongbochen

What happens if the name of the file contains spaces, or characters such as `*`? What happens if the file has 10-19, or 100-199 lines? – Tom Fenech Jan 25 '16 at 09:55
This needs you to add regular expression in the bash shell. – hongbochen Jan 25 '16 at 11:21

Black · Accepted Answer · 2016-12-14T07:23:52.580

1

I solved it with this command:

wc -l foo.txt | awk '{ print $1 }'

Output: 1

wc -l bar.txt | awk '{ print $1 }'

Output: 2

This shows the number of lines, in a script I can check wheter this number is bigger than 1 or not and my problem is solved.

edited Dec 14 '16 at 07:23

answered Jan 25 '16 at 08:55

Black

2

Use `wc -l < bar.txt` - there's no need for awk here at all. – Tom Fenech Jan 25 '16 at 08:55
1

Broken. Counts newlines rather than lines. echo -n -e 'ab\ncd' | wc -l reports just 1, though there are two lines. – DepressedDaniel Dec 14 '16 at 03:10

score 0 · Answer 3 · answered Jan 25 '16 at 08:40

0

You could do something like this:

cat foo.txt | wc -l

This would read the file and return a count of the lines within the file.

cat - read the file piped into wc (word count) -l (No. of lines)

answered Jan 25 '16 at 08:40

thonnor

2

this is a [useless use of cat](https://en.wikipedia.org/wiki/Cat_%28Unix%29#Useless_use_of_cat) – mata Jan 25 '16 at 08:47
1

Why not just `wc -l foo.txt` or `wc -l < foo.txt` ? – dreamlax Jan 25 '16 at 08:51

3 Answers3