[SOLVED] calling sleep from an awk script

Question

I am working on an awk script which repeatedly does some work and then sleeps.  Most of the time it is sleeping and while it is sleeping I would like to be able to hit control-c to abort the program.  Example awk scripts I have seen suggest this should be possible by testing for a non-zero exit code from the sleep call.  However, it doesn't work and my program won't let me stop it.  The following test program prints "0" whether I abort the sleep with control-c or wait for it to terminate normally:
#!/bin/awk -f
BEGIN {
print system("sleep 10")
My arch system is up to date.  From the "info" man page for sleep it says an abnormal termination should yield a non-zero exit code.  I've tried calling other programs instead of sleep and they return non-zero exit codes when I hit control-c on them.  I've tried invoking as "/bin/sleep 10" and "env sleep 10" as well.  Nothing works.  Any idea what I'm doing wrong?
Last edited by scottfial (2010-07-09 08:05:35)

Answer 1

Sleep must return something useful when you it ^C because the following lua program:
#!/usr/bin/lua
local exit_code
repeat
exit_code = os.execute("sleep 10")
print("exit_code: " .. exit_code)
until exit_code ~= 0
produces the following output if I let the sleep expire twice and then hit ^C:
exit_code: 0
exit_code: 0
^Cexit_code: 2
and then it terminates.  Now here's an equivalent awk program:
#!/bin/awk -f
BEGIN {
do {
exit_code = system("sleep 10")
print "exit_code: " exit_code
} while (!exit_code)
It produces the following if I let the sleep expire twice and then hit ^C twice:
exit_code: 0
exit_code: 0
^Cexit_code: 0
^Cexit_code: 0
and it never terminates.  I have to kill it.  Just to make sure that awk is seeing exit codes, I compiled this C program
int main(int argc, char *argv[]) {
return 2;
and changed my awk program to call "a.out" rather than "sleep 10".  The result is
exit_code: 2
and then it terminates.
I got the following on the command line:
$ ./a.out
$ echo $?
2
$ sleep 10
^C
$ echo $?
130
Excuse me?  130?  Lua saw a 2.  None of this makes sense.   Its as if awk has singled out "sleep" to not work!  Where am I going wrong?
Last edited by scottfial (2010-06-22 17:18:54)