bash read Frustration

[SamBones]

Ok, I'm mostly comfortable with the Korn shell. Since I'm doing some stuff on Linux now I'm trying to use bash a bit more. I'm finding that the '[tt]read[/tt]' command seems broken.

This test script in Korn shell works great...

#!/bin/ksh

echo $SSH_CONNECTION | read FROM_IP FROM_PORT TO_IP TO_PORT

echo "SSH_CONNECTION = '${SSH_CONNECTION}'"
echo "From = ${FROM_IP}:${FROM_PORT}"
echo "  To = ${TO_IP}:${TO_PORT}"

[bones@flea ~]$ ./test.ksh
SSH_CONNECTION = '10.8.24.105 58993 10.8.24.54 22'
From = 10.8.24.105:58993
  To = 10.8.24.54:22

Everything working as expected.

Same code in [tt]bash[/tt], not so much...

#!/bin/bash

echo $SSH_CONNECTION | builtin read FROM_IP FROM_PORT TO_IP TO_PORT

echo "SSH_CONNECTION = '${SSH_CONNECTION}'"
echo "From = ${FROM_IP}:${FROM_PORT}"
echo "  To = ${TO_IP}:${TO_PORT}"

[bones@flea ~]$ ./test.bash
SSH_CONNECTION = '10.8.24.105 58993 10.8.24.54 22'
From = :
  To = :

I did find online that even though [tt]read[/tt] is a shell builtin command, [tt]bash[/tt] runs it as a subprocess if used in a pipe, thus no variables defined in the parent process. Uh, that effectively breaks it.

I did find that there was a [tt]/usr/bin/read[/tt] that looked like this...

#!/bin/sh
builtin read "$@"

So I renamed that out of the way, so it's no longer there...

[bones@flea ~]$ which read
/usr/bin/which: no read in (/usr/lib64/qt-3.3/bin:/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/opt/mssql-tools/bin)

The above scripts run exactly the same, [tt]ksh[/tt] as expected, [tt]bash[/tt] broken.

I do have workarounds, but I like this construct. Piping to a [tt]read[/tt] to parse a line is very clean and easy to understand and support. Playing games with [tt]awk[/tt] or [tt]sed[/tt] to parse a line is, well, stupid.

So, all you [tt]bash[/tt] aficionados, am I missing something, or should I stick with the Korn shell?

 

[feherke]

Hi

Use a here-string :

[b]builtin read[/b] FROM_IP FROM_PORT TO_IP TO_PORT [teal]<<<[/teal] [i][green]"$SSH_CONNECTION"[/green][/i]

Though did not got why you use the [tt]builtin[/tt] keyword.


Feherke.
feherke.github.io

 

[SamBones]

Yeah, with or without "[tt]builtin[/tt]", it still doesn't work as it should. I was just trying that because the [tt]/usr/bin/read[/tt] version had it.

#!/bin/sh
[b]builtin[/b] read "$@"