Anything between those is your program

...which while block buffered, on my box is optimized into a single write() system call ;-)

strace perl -le 'INIT{ print "About to start running code" }
END{print "code ending"}
print "hello"' 2>&1 | less
execve("/usr/bin/perl", ["perl", "-le", "INIT{ print \"About to start 
+runn"...], [/* 51 vars */]) = 0
brk(0)                                  = 0x1bc9000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 
+0) = 0x7fc0fdf2f000
...
rt_sigaction(SIGIO, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGSYS, NULL, {SIG_DFL, [], 0}, 8) = 0
write(1, "About to start running code\nhell"..., 46About to start runn
+ing code
hello
code ending
) = 46
exit_group(0)                           = ?
+++ exited with 0 +++
[download]

I wished only half of the programs in my linux distro were half as good as the perl optimizer. Not to mention the stuff I am perlpetrating :)

He can use warn or print STDERR to prevent that.

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

Of course. Setting $| to true also helps. TIMTOWTDI :-)

That was a really eloquent solution!

Unfortunately I think my reading stdout with pipes is flawed! :( I get all the "starting" "hello" and "ending code" just all together after all the 367 system calls and printed.

And this is because I'm reading the pipes after the program exits

Any ideas for other approaches?

Thanks for your answer though! After 1 month of side lining this I realize today my approach is slightly flawed!

Unfortunately I think my reading stdout with pipes is flawed!

Not necessarily so. More probably you are "suffering from buffering":

• printing to the terminal is line buffered
• printing elsewhere is block buffered

Try inserting

$| = 1;
[download]

at the top of your program. See perlvar.

I get all the "starting" "hello" and "ending code" just all together after all the 367 system calls and printed.

Replace print with print STDERR ...; (or use warn).

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

So I rewrote the perl program and the C program to write to the same text file

I get something like this in my output.txt:

237 time system call 8
238 time system call 8
239 time system call 5
240 time system call 5
241 time system call 72
242 time system call 72
243 time system call 1
Started #The BEGIN block
244 time system call 1
245 time system call 3
246 time system call 3
247 time system call 2
248 time system call 2
249 time system call 8
250 time system call 8
251 time system call 16
252 time system call 16
253 time system call 8
254 time system call 8
255 time system call 5
256 time system call 5
257 time system call 72
258 time system call 72
259 time system call 1
hello world
260 time system call 1
261 time system call 3
262 time system call 3
....
....
At 400 about I get the END block print
and then 3 more system calls before termination
[download]

Unfortunately I don't know now when I should start monitoring the target problem. I want to write something of a generic tracer for any perl script. I thought I would see a pattern in the perl interpreter's system calls but I don't. Any ideas?

What BrowserUk says - use INIT, not BEGIN, since BEGIN blocks are executed in the compile phase of the perl script.

I want to write something of a generic tracer for any perl script.

Why? GNU/Linux has tools for that ready - strace(1), ltrace(1). I suspect an XY problem here. What are you trying to to with that which you are ostensibly trying to do?

Then, perl is linked against many libraries, and it can well be that most of those syscalls happen inside calls to functions in these libraries. To verify that, you can use ltrace(1), which displays library calls, together with the -S switch to display system calls as well.

use INIT, not BEGIN

Yes, it is INIT not begin. I put in a typo. Sorry!

I suspect an XY problem here. What are you trying to to with that which you are ostensibly trying to do?

Oh, no no! It's not. I'm just trying to learn how a debugger is built :) I downloaded the source for strace and gdb but it's just too large to understand..

Mostly, it's a exercise in perl, C and Linux I've given myself to write a program that can list out all system calls a perl script is making while executing that program .

The only thing I would add is that I recommended INIT and END; not BEGIN and END; and that difference may well account for much of your syscall activity, as modules files are read and parsed and memory allocated to accommodate them.

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

I cannot help you with that as I don't run *nix.

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.