shell script does not read last line from sysin

Question

I try to get some data from sysin and here is my problem: if data are directed from a file, then the last line is not read. Example of text file:

line1
line2
line3

My code:

#!/bin/bash
while read line
do
  echo "$line"
done

And output:

$ ./test.sh < data.txt
line1
line2

If I write down at the end of my file null string output correct. But I don`t like it. How to fix this?

There are **lots** of duplicates for this one. Are you sure you tried to search for an existing answered question? See also: http://stackoverflow.com/questions/15485555/read-last-line-of-file-in-bash-script-when-reading-file-line-by-line, http://stackoverflow.com/questions/4165135/how-to-use-while-read-bash-to-read-the-last-line-in-a-file-if-there-s-no-new, http://stackoverflow.com/questions/16627578/bash-iterating-through-txt-file-lines-cant-read-last-line — Charles Duffy, May 07 '16 at 17:58

score 2 · Answer 1 · answered May 07 '16 at 17:55

The idiom for this is:

while read -r line || [[ $line ]]; do
  : process "$line"
done

Thus, we proceed in the loop while either:

We read a valid line of text (which requires a newline)
We had a partial read (which results in a nonzero exit status, but leaves the variable non-empty).

score 1 · Accepted Answer · answered May 07 '16 at 17:54

1

If you need desperately to read files without EOL in the end, then you may check whether returned string is empty or not instead of checking read exit status:

#!/bin/bash
while true; do
  line=''
  read line
  if [ -z "$line" ]; then
    break
  fi
  echo "$line"
done

answered May 07 '16 at 17:54

gudok

4,029
2
20
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Works, but quite considerably more verbose than it needs to be. – Charles Duffy May 07 '16 at 18:19

score 0 · Answer 3 · answered May 07 '16 at 17:46

0

I bet you that data.txt is missing a trailing newline, try checking with

od -xa data.txt

Look at the end:

$ od -xa data.txt
0000000    696c    656e    0a31    696c    656e    0a32    696c    656e
          l   i   n   e   1  nl   l   i   n   e   2  nl   l   i   n   e
0000020    0033
          3
0000021

If you see the above you are missing the newline.

$ od -xa data-with-nl.txt
0000000    696c    656e    0a31    696c    656e    0a32    696c    656e
          l   i   n   e   1  nl   l   i   n   e   2  nl   l   i   n   e
0000020    0a33
          3  nl
0000022

Some shells will also show a % sign if trailing newline is missing, try:

$ cat data.txt
line1
line2
line3%
$

answered May 07 '16 at 17:46

Andreas Louv

46,145
13
104
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Exactly! But how to change my codethis situation? How to finish read file on EOF? – Nawy May 07 '16 at 17:50
@Nawy What? You want to add the newline to `data.txt`? – Andreas Louv May 07 '16 at 17:52
no, I don`t. I just want to process file without newline at the end of file – Nawy May 07 '16 at 18:04

shell script does not read last line from sysin

3 Answers3