[SOLVED] Can an awk script find its own name?

catkin · 05-13-2011, 02:23 PM

Hello

According the The GNU Awk User's Guide "the value of ARGV[0] (see Built-in Variables) varies depending upon your operating system. Some systems put ‘awk’ there, some put the full pathname of awk (such as /bin/awk), and some put the name of your script (‘advice’). Don't rely on the value of ARGV[0] to provide your script name".

So is there any way for an executing awk script find its own name? AFAIK it has no way to determine its own PID so it can't use the process table via ps ...

Best

Charles

druuna · 05-13-2011, 02:49 PM

Hi,

Didn't know this myself, but was intrigued by the question, a search came up with this:

Code:

BEGIN { getline t < "/proc/self/cmdline";split(t,T,"\0")
print "My name is:",T[3] }

Test run:

Code:

gawk -f myfile 
My name is: myfile

mv myfile /tmp/
gawk -f /tmp/myfile 
My name is: /tmp/myfile

Hope this helps.

grail · 05-14-2011, 12:10 AM

Here is another option for you, although you can use your favourite way to use a pid to get the name:

Code:

BEGIN{ cmd = "ps -p "PROCINFO["pid"]" -o comm="; print | cmd }

The difference here is that the script being called in druuna's fashion will yield gawk whereas:

Code:

#!/usr/bin/awk -f

<blah>

And called as:

Code:

./script.awk

Will get you script.awk

druuna · 05-14-2011, 02:41 AM

@grail,

Maybe I misunderstand what you are saying, but my posted solution works both ways:

- Code is in a separate file, called by (g)awk (see post #2 for example),

- Code is part of a (g)awk script.

Code:

$ cat foo.awk
#!/usr/bin/awk -f

BEGIN { getline t < "/proc/self/cmdline";split(t,T,"\0")
print "My name is:",T[3] }

$ ./foo.awk
My name is: ./foo.awk

catkin · 05-14-2011, 03:31 AM

Thanks both

Despite scouring the awk man page for an equivalent of bash' $$ I had not found PROCINFO["pid"]

so that was useful to learn.

I could not get the ps solution to work because the COMM field was not wide enough for my script's name and attempts to widen the column were not effective (-o comm:<big number>, -w option). Using cmd instead of comm worked but gave a space-separated list which would break if there was a space in the pathname so I chose the /proc method (which will (?) break for NULs in the pathname but that's acceptable).

Here's the final solution, adapting drunna's method to my verbose style that puts clarity above conciseness:

Code:

    getline cmdline < "/proc/self/cmdline"
    split( cmdline, array, "\0" )
    My_name = substr( array[3], match( array[3], /\/[^\/]*$/ ) + 1 )

Best

Charles

syg00 · 05-14-2011, 03:51 AM

Surely you're not suggesting drunna has provided a less than effusive answer .... ????

ROTFL ...

catkin · 05-14-2011, 04:07 AM

Quote:

Originally Posted by syg00

Surely you're not suggesting drunna has provided a less than effusive answer .... ????

ROTFL ...

Well, my code has longer variable names, more lines and more spaces ...

EDIT: regards coding style do are we establishing a terseness to verbosity spectrum going from grail via drunna to me?

grail · 05-14-2011, 04:18 AM

Trust me to be on the bottom rung ... sheesh ... LOL

Nominal Animal · 05-14-2011, 11:11 AM

Quote:

Originally Posted by catkin

attempts to widen the column were not effective (-o comm:<big number>, -w option)

To widen ps output, you need to set the COLUMNS environment variable: env COLUMNS=4096 ps ...

catkin · 05-15-2011, 12:02 AM

Thanks Nominal Animal

but it didn't work in this case

Code:

c@CW8:~$ ps -p1961 -f
UID        PID  PPID  C STIME TTY          TIME CMD
root      1961     1  0 10:13 ?        00:00:00 /usr/sbin/console-kit-daemon --no-daemon
c@CW8:~$ ps -p1961 -o comm=
console-kit-dae
c@CW8:~$ export COLUMNS=4096
c@CW8:~$ ps -p1961 -o comm=
console-kit-dae

catkin · 05-15-2011, 12:04 AM

Quote:

Originally Posted by grail

Trust me to be on the bottom rung ... sheesh ... LOL

OK, a verbose to terse spectrum going from me via drunna to grail

grail · 05-15-2011, 01:33 AM

So top to bottom still puts me down there .. hehe