bash while loop drops last line of text file [dupl

问题:

This question already has answers here:

Shell script read missing last line (7 answers)

Closed 2 years ago.

when i cat this file I get 6 lines (it is a diff file)

bash-3.00$ cat /tmp/voo
18633a18634
> sashabSTP
18634a18636
> sashatSTP
21545a21548
> yheebash-3.00$

however when i read it line by line i only get 5 lines.

bash-3.00$ while read line ; do echo $line ; done < /tmp/voo
18633a18634
> sashaSTP
18634a18636  
> sashatSTP
21545a21548

or this

bash-3.00$ cat /tmp/voo | while read line ; do  echo $line ; done
18633a18634
> sashabSTP
18634a18636
> sashatSTP
21545a21548
bash-3.00$

i am missing the last line 'yhee' from the while loops.

回答1:

Note:

21545a21548
> yheebash-3.00$
      ^---- no line break

Your file doesn't terminate with a line break.

回答2:

If you are wondering why?, this might satisfy your curiosity.

If you work with files which may or may not end up with a new line at end, you can do this:

while IFS= read -r line || [ -n "$line" ]; do
  echo "$line"
done <file

Or this:

while IFS= read -r line; do
  echo "$line"
done < <(grep "" file)

Read more:

1. https://stackoverflow.com/a/31397497/3744681
2. https://stackoverflow.com/a/31398490/3744681