Error transporting binary data over ssh/telnet (even shell) in expect script

[fangxlmr]

It seems like no one is maintaining this repo any more, but I still wanna post the issue here since it confuse me a lot and closely releated to expect command. Assuming I'd like to fetch data from remote with user/password auth automating in expect script, like the following: ps: I use sh to refer ssh/telnet connection

$ expect -v
expect vesion 5.45.4
$ cat expect.sh
#!/usr/bin/expect -f

spawn -noecho sh -c ./download.sh
interact
$ cat download.sh
#!/bin/sh

sh -c 'cat /bin/ls' # cat a binary file
$ ./expect.sh > a.out
$ file a.out
a.out: ELF 64-bit LSB shared object, x86-64, version1 (SYSV), too many program (2304)

As the last command said, captured command ls (i.e. a.out) has broken locally. And you can find if you actually run the script, the two files are different in bytesize (let alone checksum).

I though it might be related to traslation and encoding issue, so I change the expect.sh script to this and it still not working

$ cat expect.sh
#!/usr/bin/expect -f

spawn -noecho sh -c ./download.sh
fconfigure $spawn_id -translation binary -encoding binary
fconfigure stdin -translation binary -encoding binary
fconfigure stdout -translation binary -encoding binary
interact

Any body has any idea?

[clarkwang]

xref: https://stackoverflow.com/questions/65436528/

[douniwan5788]

1. Use stty raw to disable all translations
2. export LC_ALL=en_US.ISO-8859-1 to avoid encoding problems with expect

[fangxlmr]

xref: https://stackoverflow.com/questions/65436528/

@clarkwang Thanks. Indeed, the question on Stackoverflow is posted by me as well.

[fangxlmr]

@douniwan5788 Yes! That does work! Thanks!

One more question: Since I wanna keep the 'newline' symbol as whatever it is, how to avoid \r\n translation?

This might happen when cat a binary data. Binary data might contain byte 0a (i.e. \n) so that expect converts it to 0d0a (i.e. \r\n) resulting in broken binary as well.

[fangxlmr]

spawn "telnet xxx"
fconfigure $spawn_id -translation crlf

focnfigure command seems solve the translation issue.