[Bash] output of command in infinite loop

[peer]

I have a 'dvb-t dab fm' usb stick thas has a IR receiver in it. With this receiver I can read the codes that are send from a remote control. In bash I use the command: '/usr/bin/ir-keytable -s rc0 -t'. This command waits for a button press and then shows the code in the terminal. It is stopped with CTRL-C.
Her is an example of the output:

Code: Select all

/usr/bin/ir-keytable -s rc0 -t
Testing events. Please, press CTRL-C to abort.
653.122133: lirc protocol(rc5): scancode = 0xc toggle=1
653.122142: event type EV_MSC(0x04): scancode = 0x0c
653.122142: event type EV_SYN(0x00).
653.334160: lirc protocol(rc5): scancode = 0xc toggle=1
653.334169: event type EV_MSC(0x04): scancode = 0x0c
653.334169: event type EV_SYN(0x00).
^C

I would like to make a script that after each keypress show the protocol and the scancode. So I need to redirect the output to a variable. How can I do this?

[CwF]

So I need to redirect the output to a variable. How can I do this?

I think I would output to a file, likely append, then separately read the last line.

I've had this thought for dissecting am HD-Radio module that is partial figured out. Also, is the IR part of the dongle or a cabled in extra? I have a few such gadgets that were not recognized years ago and haven't played with them since. The hauppauge's I currently use have an IR section I should investigate someday...

[steve_v]

Generally, one might use a while loop, a pipe, and the 'read' builtin, like:

Code: Select all

<some command>  |
while IFS= read -r line; do
    <do something with $line>
done

Where each line of stdout from <some command> is placed in the variable $line.
Setting IFS (to null) should prevent word-splitting on spaces in the command output, similarly the '-r' option to read prevents interpretation of escape characters.

Many manuals and tutorials exist covering this.

[peer]

So I need to redirect the output to a variable. How can I do this?

I think I would output to a file, likely append, then separately read the last line.

I've had this thought for dissecting am HD-Radio module that is partial figured out. Also, is the IR part of the dongle or a cabled in extra? I have a few such gadgets that were not recognized years ago and haven't played with them since. The hauppauge's I currently use have an IR section I should investigate someday...

The IR is part of the dongle

I tried to redirect the output to a file. I tried both:

Code: Select all

/usr/bin/ir-keytable -s RC0 -t > test.txt      and
/usr/bin/ir-keytable -s RC0 -t >> test.txt

The file test.txt is created but the size = o.

[peer]

Generally, one might use a while loop, a pipe, and the 'read' builtin, like:

Code: Select all

<some command>  |
while IFS= read -r line; do
    <do something with $line>
done

Where each line of stdout from <some command> is placed in the variable $line.
Setting IFS (to null) should prevent word-splitting on spaces in the command output, similarly the '-r' option to read prevents interpretation of escape characters.

Many manuals and tutorials exist covering this.

I tried:

Code: Select all

/usr/bin/ir-keytable -s RC0 -t |
while IFS= read -r line; do
    echo $lin>
done

There is no output at all

[peer]

I think redirecting does not work with the command '/usr/bin/ir-keytable -s RC0 -t'. The command listens to the remote control and gives output when a button is pressed on the remote. This is done during the execution of the command, not after.
I tried the scripting method:

Code: Select all

/usr/bin/script -c "/usr/bin/ir-keytable -s RC0 -t"test.txt

Now the test.txt file is created and is showing the output but only after the command is finished. And I would like access to the output during the execution of the command

[lindi]

You could try the -f option of script.

[peer]

Yes, that works!
Now I have the following command:

Code: Select all

/usr/bin/script -c "/usr/bin/ir-keytable -s RC0 -t" test.txt -f

When I press a button on the remote there are a few lines added to the file test.txt.