Why is this regex not catching the last line of a file?

Question

I read a text file line by line in a bash script, the goal is to catch variable declarations.

The bash script:

#!/bin/bash

filePath=$1

while read line
do
    if [[ $line =~ ^[[:blank:]]*([^#[:blank:]]+)[[:blank:]]*=[[:blank:]]*(.*) ]]
    then
        var=${BASH_REMATCH[1]}
        value=${BASH_REMATCH[2]}
        echo "$var=$value"
    fi
done < "$filePath"

With this text file (note that the line "c=3" is the last line of the file):

# First variable
a=1
# Second variable
 b = 2
# Third variable
c=3

The output is:

a=1
b=2

But with this one:

# First variable
a=1
# Second variable
 b = 2
# Third variable
c=3
# empty line

The output is:

a=1
b=2
c=3

It can be an empty line at the end, not necessary a comment.

Can someone explain why the last line is not catched by the regex in the first example? And how can I fix the problem (except from adding an empty line at the end of the text file...)? Thanks

Does your first file have a linebreak at the end? (Test with `cat -A`, check for end-of-line markers.) I suspect it doesn't. — Benjamin W., Mar 14 '17 at 14:39
And if this is the problem, the solution is http://stackoverflow.com/questions/12916352/shell-script-read-missing-last-line: `while read line || [[ -n $line ]]` — Benjamin W., Mar 14 '17 at 14:39
Wow! This is it, and your solution works perfectly! Thank you so much! — scandel, Mar 14 '17 at 14:53
More fundamentally, maybe ask yourself if this makes sense as a Bash script. Perhaps Awk would be more versatile as well as straightforward. — tripleee, Mar 15 '17 at 04:47
@tripleee maybe you're right, but what I shown is just a part of a bigger script, and I believe bash is a correct choice. Furthermore, I didn't wrote it in the first place ! — scandel, Mar 15 '17 at 08:43

beliy · Answer 1 · 2017-03-14T15:31:25.263

0

for while read line; do ... ; doneyour file need end with a newline.

try:

while IFS= read -r line || [ -n "$line" ]; do

edited Mar 14 '17 at 15:31

answered Mar 14 '17 at 14:57

beliy

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[Don't read lines with `for`](http://mywiki.wooledge.org/DontReadLinesWithFor). – Benjamin W. Mar 14 '17 at 15:01
thanks, you right... im edited my post... – beliy Mar 14 '17 at 15:24
But then you still don't read the last line if it doesn't end with a newline character, so you need `while IFS= read -r line || [[ -n $line ]]; do` – Benjamin W. Mar 14 '17 at 15:28
2

...and then you have the exact answer from the duplicate ;) – Benjamin W. Mar 14 '17 at 15:28
yeap, you right again) – beliy Mar 14 '17 at 15:32

Why is this regex not catching the last line of a file?

1 Answers1