Simple question about capturing output to /dev/tty

Firerat · 07-15-2013, 07:25 PM

Quote:

Originally Posted by Paul R

Well, I logged in as root (using sudo), ran strace, and it no longer gave me the previous error... However, now I get a different error...

# strace ./tst 2> tst.out2
# cat tst.out2
ERROR: tracer already exists

I'm lost with that one...

shame as
write(1, "1234\n"
is what you need from strace

Paul R · 07-15-2013, 07:28 PM

Well, that's pretty cool output from strace. From there, it would be a simply matter of parsing out the "write" lines, which contain the data that is written to /dev/tty. It's a great idea. I only wish strace worked on my system! I can try to touch base with my UNIX admin to see why it's not working, but... it's always real hard to get ahold of him. Any OTHER suggestions??? --Paul.

Quote:

Originally Posted by Firerat

strace, on tst ( with shabang )

Code:

open("./tst", O_RDONLY)                 = 3
fcntl(3, F_DUPFD, 10)                   = 10
close(3)                                = 0
fcntl(10, F_SETFD, FD_CLOEXEC)          = 0
rt_sigaction(SIGINT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGINT, {0x40f270, ~[RTMIN RT_1], SA_RESTORER, 0x7f25d83b6260}, NULL, 8) = 0
rt_sigaction(SIGQUIT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGQUIT, {SIG_DFL, ~[RTMIN RT_1], SA_RESTORER, 0x7f25d83b6260}, NULL, 8) = 0
rt_sigaction(SIGTERM, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGTERM, {SIG_DFL, ~[RTMIN RT_1], SA_RESTORER, 0x7f25d83b6260}, NULL, 8) = 0
read(10, "#!/bin/sh\necho 1234 > /dev/tty\n\n", 8192) = 32
open("/dev/tty", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3
fcntl(1, F_DUPFD, 10)                   = 11
close(1)                                = 0
fcntl(11, F_SETFD, FD_CLOEXEC)          = 0
dup2(3, 1)                              = 1
close(3)                                = 0
write(1, "1234\n", 51234
)                   = 5
dup2(11, 1)                             = 1
close(11)                               = 0
read(10, "", 8192)                      = 0
exit_group(0)                           = ?

Paul R · 07-15-2013, 07:53 PM

Well... I got truss to work, but the "write" line is not as elegant... it puts a bunch of stupid spaces in...

fcntl(3, F_DUPFD, 0x00000001) = 1
close(3) = 0
write(1, " 1 2 3 4 5 6 7 8 9\n", 12) = 12
fcntl(1, F_GETFD, 0x00000000) = 0
close(1) = 0
fcntl(10, F_DUPFD, 0x00000001) = 1

But at least I have something to work with now. --Paul.

Quote:

Originally Posted by Paul R

Well, that's pretty cool output from strace. From there, it would be a simply matter of parsing out the "write" lines, which contain the data that is written to /dev/tty. It's a great idea. I only wish strace worked on my system! I can try to touch base with my UNIX admin to see why it's not working, but... it's always real hard to get ahold of him. Any OTHER suggestions??? --Paul.

Firerat · 07-15-2013, 07:59 PM

Quote:

Originally Posted by Paul R

Well... I got truss to work, but the "write" line is not as elegant... it puts a bunch of stupid spaces in...

Code:

fcntl(3, F_DUPFD, 0x00000001)                   = 1
close(3)                                        = 0
write(1, " 1 2 3 4   5 6 7 8   9\n", 12)        = 12
fcntl(1, F_GETFD, 0x00000000)                   = 0
close(1)                                        = 0
fcntl(10, F_DUPFD, 0x00000001)                  = 1

But at least I have something to work with now. --Paul.

I was just about to come back with truss, ( after startpaging the error you were getting )

You just need to get out the ol' awk now

Paul R · 07-16-2013, 02:18 AM

Well... I spoke too soon, because I tested too few characters with truss. Here is what the actual output looks like from the license tool:

License activity on ihgp:

Feature in use total occupancy
----------------- ------ ----- ---------
6000 24 97 25%
6001 0 3 0%
6005 0 1 0%

And here is what the truss output looks like:

11486: write(1, "\n L i c e n s e a c t".., 28) = 28
11486: write(1, " F e a t u r e ".., 45) = 45
11486: write(1, " - - - - - - - - - - - -".., 45) = 45
11486: write(1, " 6 0 0 0 ".., 43) = 43
11486: write(1, " 6 0 0 1 ".., 43) = 43
11486: write(1, " 6 0 0 5 ".., 43) = 43

As you can see, major truncation... to the point where the output is basically useless (there are lots of spaces in the output, but this forum software is scrunching them down to one space). I searched the man page and internet for a solution, but did not find any. Any ideas? --Paul.

Quote:

Originally Posted by Firerat

I was just about to come back with truss, ( after startpaging the error you were getting )

You just need to get out the ol' awk now

NevemTeve · 07-16-2013, 02:38 AM

It is not easy to find out what the actual question is... the OP seems to keep changing his or her question constantly. If the (current) question is about redirecting a program's output from /dev/tty into file, that would be something like this:

Code:

script -q -c "echo 'Hi'>/dev/tty" ttyoutput.txt >/dev/null

catkin · 07-16-2013, 03:10 AM

But script captures terminal sessions and the problem binary is not running a terminal session.

AFAIK the OP has been completely consistent in wanting to find a way to capture what is being written to the virtual device /dev/tty.

The screen command should be good for that. I have never used screen so cannot advise how.

Firerat · 07-16-2013, 03:35 AM

Quote:

Originally Posted by Paul R

Well... I spoke too soon, because I tested too few characters with truss. Here is what the actual output looks like from the license tool:

Code:

License activity on ihgp:

Feature               in use    total   occupancy
-----------------     ------    -----   ---------
6000                      24       97      25%
6001                       0        3       0%
6005                       0        1       0%

And here is what the truss output looks like:

Code:


11486:  write(1, "\n L i c e n s e   a c t".., 28)      = 28
11486:  write(1, " F e a t u r e          ".., 45)      = 45
11486:  write(1, " - - - - - - - - - - - -".., 45)      = 45
11486:  write(1, " 6 0 0 0                ".., 43)      = 43
11486:  write(1, " 6 0 0 1                ".., 43)      = 43
11486:  write(1, " 6 0 0 5                ".., 43)      = 43

As you can see, major truncation... to the point where the output is basically useless (there are lots of spaces in the output, but this forum software is scrunching them down to one space). I searched the man page and internet for a solution, but did not find any. Any ideas? --Paul.

[ c o d e ]
Preserves
indents and the like
[ / c o d e ]
http://www.linuxquestions.org/questi....php?do=bbcode

Code:

Preserves
    indents and the like

Anyway, they spaces are not a problem,,

This is crude, but should work

Code:

awk -F\" '/write/{gsub(/  /,"_");gsub(/ /,"");gsub(/_/," ");print $2}' Input.file

replacing all double spaces with _
deleting all single spaces
then replacing all _ with space.

Probably better ways to do it, but it works well for now

BUT, I don't see the numbers you want...

http://www.idevelopment.info/data/Un...nSolaris.shtml

Code:

 Using truss

Truss is used to trace the system/library calls (not user calls) and signals made/received by a new or existing process. It sends the output to stderr.

    NOTE: Trussing a process throttles that process to your display speed. Use -wall and -rall sparingly. 

Truss usage

    truss  -a  -e  -f  -rall  -wall  -p  
    truss  -a  -e  -f  -rall  -wall  

    -a        Show arguments passed to the exec system calls
    -e        Show environment variables passed to the exec system calls
    -f        Show forked processes 
                (they will have a different pid: in column 1)
    -rall     Show all read data (default is 32 bytes)
    -wall     Show all written data (default is 32 bytes) 
    -p        Hook to an existing process (must be owner or root)
    <program> Specify a program to run

so it looks like if you add -wall to the truss you will get all the write, not just first 32 bytes

NevemTeve · 07-16-2013, 03:51 AM

> But 'script' captures terminal sessions and the problem binary is not running a terminal session.

Methinks if it weren't running in a terminal session, writing on '/dev/tty' wouldn't work.

bonnydeal · 07-16-2013, 07:43 AM

You can use 'expect' for this.
It may already be on your system.

If not get it here:
http://expect.sourceforge.net

Paul R · 07-16-2013, 10:35 AM

Duh... I had been using the -w!all option instead of -wall. Thanks! :-)

Quote:

Originally Posted by Firerat

BUT, I don't see the numbers you want...

http://www.idevelopment.info/data/Un...nSolaris.shtml

Code:

 Using truss

Truss is used to trace the system/library calls (not user calls) and signals made/received by a new or existing process. It sends the output to stderr.

    NOTE: Trussing a process throttles that process to your display speed. Use -wall and -rall sparingly. 

Truss usage

    truss  -a  -e  -f  -rall  -wall  -p  
    truss  -a  -e  -f  -rall  -wall  

    -a        Show arguments passed to the exec system calls
    -e        Show environment variables passed to the exec system calls
    -f        Show forked processes 
                (they will have a different pid: in column 1)
    -rall     Show all read data (default is 32 bytes)
    -wall     Show all written data (default is 32 bytes) 
    -p        Hook to an existing process (must be owner or root)
    <program> Specify a program to run

so it looks like if you add -wall to the truss you will get all the write, not just first 32 bytes

Paul R · 07-16-2013, 10:41 AM

I have "expect" on my system, and read similar suggestions on the internet for others who had the same problem as me, but... I'm not sure I understand it, and have never seen any coding examples. So... If YOU were dealing with someone elses one-line script that wrote to /dev/tty (i.e. echo "1234" > /dev/tty), then how would YOU capture the "1234" output using expect? I'm open to any/all suggestions/solutions, because even though truss seems to work, it may NOT work in a cronjob (which I haven't tested yet). If need be, I can run a script from the UNIX prompt, and append "&" to run it in the background (indefinitely), but I would prefer running a cron job periodically instead. -Paul.

Quote:

Originally Posted by bonnydeal

You can use 'expect' for this.
It may already be on your system.

If not get it here:
http://expect.sourceforge.net

Kustom42 · 07-16-2013, 12:23 PM

Quote:

Originally Posted by Paul R

I have "expect" on my system, and read similar suggestions on the internet for others who had the same problem as me, but... I'm not sure I understand it, and have never seen any coding examples. So... If YOU were dealing with someone elses one-line script that wrote to /dev/tty (i.e. echo "1234" > /dev/tty), then how would YOU capture the "1234" output using expect? I'm open to any/all suggestions/solutions, because even though truss seems to work, it may NOT work in a cronjob (which I haven't tested yet). If need be, I can run a script from the UNIX prompt, and append "&" to run it in the background (indefinitely), but I would prefer running a cron job periodically instead. -Paul.

From what I've seen you still haven attempted the command substitution which I have tested and verified works. I have no idea how expect would be useful here, I use expect to enter passwords in ssh for loops and so on.

Here is an example:

Code:

#!/usr/bin/expect

set logfile [open /tmp/iplist]
set ipaddrs [read $logfile]
set timeout 45

foreach ip [split $ipaddrs \n] {

        set pass "PASSWORDHERE"
       spawn ssh root@$ip "yum install -y openldap-clients nss_ldap"
       expect {
        password: {send "$pass\r"; exp_continue}
                }
}

That does an ssh loop and sends a password which installed nss_ldap in my environment. Now unless I'm missing something here, expect would be of no use to you for this situation.

Firerat · 07-16-2013, 01:21 PM

Quote:

Originally Posted by Paul R

I have "expect" on my system, and read similar suggestions on the internet for others who had the same problem as me, but... I'm not sure I understand it, and have never seen any coding examples. So... If YOU were dealing with someone elses one-line script that wrote to /dev/tty (i.e. echo "1234" > /dev/tty), then how would YOU capture the "1234" output using expect? I'm open to any/all suggestions/solutions, because even though truss seems to work, it may NOT work in a cronjob (which I haven't tested yet). If need be, I can run a script from the UNIX prompt, and append "&" to run it in the background (indefinitely), but I would prefer running a cron job periodically instead. -Paul.

I think NevemTeve's solution is the cleanest, it certainly seems to work with the "tst" script

the cronjob should simply be periodically executing a shell script, one which appends to a log.

Assuming NevemTeve's Script solution works

Code:

#!/bin/sh
# LicenseCheckLogger.sh
script -q -c /path/to/TheBin -a /path/to/logfile >/dev/null

and your cron ( every 15min )

Code:

*/15 * * * * /path/to/LicenseCheckLogger.sh

Now, if truss is what works

Code:

#!/bin/sh
# LicenseCheckLogger.sh

truss -wall /path/to/TheBin 2>&1 | \
awk -F\" 'BEGIN{"date +%Y%m%d-%R"|getline Date};/write/&&/" 6/{gsub(/  /,"_");gsub(/ /,"");gsub(/_/," ");print Date" "$2}' >> /path/to/logfile

I added a little to the awk, each line will get the date/time ( awk was started )
also limiting to 'needed' info ( starting " 6 )

bonnydeal · 07-17-2013, 07:18 AM

Quote:

Originally Posted by Paul R

I have "expect" on my system, and read similar suggestions on the internet for others who had the same problem as me, but... I'm not sure I understand it, and have never seen any coding examples. So... If YOU were dealing with someone elses one-line script that wrote to /dev/tty (i.e. echo "1234" > /dev/tty), then how would YOU capture the "1234" output using expect? I'm open to any/all suggestions/solutions, because even though truss seems to work, it may NOT work in a cronjob (which I haven't tested yet). If need be, I can run a script from the UNIX prompt, and append "&" to run it in the background (indefinitely), but I would prefer running a cron job periodically instead. -Paul.

I understand you have a script to write to tty (ttyout.sh)

Code:

#!/usr/bin/bash
# 

echo 1234 > /dev/tty

Sample expect script to capture tty (ttycap.exp)

Code:

#!/usr/bin/expect -f

#spawn the command that outputs to tty here. 
# This is just the echo 1234  in your example.
spawn ./ttyout.sh
        expect {
                eof {exit}
        }

Invocation

Code:

MYNUMBER=$(./ttycap.exp | tail -1)
echo $MYNUMBER

Expect is the best way to do this, imho, because it is specifically designed to work with tty output.
You can do it with a few lines of expect then parse the output how you like.
In the example I just used tail to get the last line, you may want to do something else.