There will be extra characters when podman run with `--tty`

[zhangguanzhang]

containers/podman#7196 (comment)

[root@sz-test ~]# podman run --rm  alpine echo 1 | cat -A
1$
[root@sz-test ~]# podman run --rm --tty alpine echo 1 | cat -A
1^M$
    [root@sz-test ~]# 

The problem seems to be here
https://github.com/containers/conmon/blob/master/src/ctr_logging.c#L355-L360
@rhatdan PTAL

[haircommander]

thanks for opening the issue @zhangguanzhang! I am not so sure it's that line in particular. if you look at the log line:

[root@sz-test overlay-containers]# cat -A 62189eb5a343e7d14e90df0f5a6d03a00fae3120fccc097ac4a5f3d47cbb9689/userdata/ctr.log
2020-08-05T13:34:22.891045849+08:00 stdout F hello^M$

we see it's a full log line (signified by the F after stdout). if it was a partial line, it would be P

If you look at that line, it checks if (partial) which means we only append the newline if it's a partial line.

I believe this line is from interpreting the terminal pipe as one. I do not think conmon can or should drop these characters. instead, could podman drop these characters if printing the logs @mheon ?

[psakar]

It happens only for one liner, it is gone in case two lines are printed

[psakar@localhost podman]$ podman run --rm --tty busybox echo 1 | cat -A
1^M$
    [psakar@localhost podman]$ podman run --rm --tty busybox echo 1 ; echo 2 | cat -A
1
2$
[psakar@localhost podman]$ 

[psakar]

podman run --rm --tty busybox echo -n 1 | cat -A also works as expected. Seems only the case when output is single line (can be empty) with new line at the end is wrong

[mheon]

Hm. Tend to agree this is Podman reading the log line incorrectly.

[giuseppe]

I think it works as expected. It is the same behavior I get with docker:

$ podman run --rm --tty busybox echo  1 | cat -A 
1^M$
# docker run --rm --tty alpine echo 1 | cat -A
1^M$

# docker run --rm --tty alpine echo -n 1 | cat -A
1
$ podman run --rm --tty busybox echo  -n 1 | cat -A 
1