Strace on a tree structure C program

When I tried to access 'unallocated node value' , as usual 'Segmentation fault' came as output :-)

But i am not fully clear on how mmap() system call allocate the memory...

I also came to know that mprotect() system call sets the protection,

If the calling process tries to access memory in a manner that violates the protection, then the kernel generates a SIGSEGV signal for the process.

Program and Strace details:

 

Try Strace on wget command

Its fun to try Strace on different commands to see what actually happens behind the command. There are some very good options to filter out required systems calls from the log.
The following link gives examples on how to use Strace http://www.thegeekstuff.com/2011/11/strace-examples/

one interesting system call is 'select' . I was only heard about 'select' in sql queries,but this is a different place i am seeing select :-)

"select() and pselect() allow a program to monitor multiple file descriptors, waiting until one or more of the file descriptors become "ready" for some class of I/O operation (e.g., input possible). A file descriptor is considered ready if it is possible to perform a corresponding I/O operation"

The sigaction() system call is used to change the action taken by a process on receipt of a specific signal.

 socket system call:

Strace experiments on Python

I was watching the video on 'Type  Python ,Press enter. What happens'. I thought of checking whether 'strace' can get the fork() system call that he explained in the video.

Unfortunately I couldn't get ....



But i came to know about the write and read system calls when we type the arithmetic operatons on python ... strace log pasted below. Still I dont know where the calculation is happening.... is there any tool to list which part is calculating it ? where is the fork() ?? brk(0x19ed000) = 0x19ed000 ioctl(0, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 ioctl(1, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 write(2, ">>> ", 4) = 4 read(0, "1+2\n", 1024) = 4 fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 6), ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f0206e7b000 write(1, "3\n", 2) = 2 ioctl(0, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 ioctl(1, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 write(2, ">>> ", 4) = 4 read(0, "1+4\n", 1024) = 4 write(1, "5\n", 2) = 2 ioctl(0, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 ioctl(1, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 write(2, ">>> ", 4) = 4 read(0,