List Processes using libproc

To learn a little more about processes on a Linux system and to try writing some code in C I adapted some code from this blogpost and wrote a super basic version of the ps command.

On Debian based Linux systems first install libproc.

$ sudo apt-get install libproc-dev

The code:

#include <stdio.h>
#include <string.h>
#include <proc/readproc.h>

int main(int argc, char** argv)
{
 // fillarg used for cmdline
 // fillstat used for cmd
 PROCTAB* proc = openproc(PROC_FILLARG | PROC_FILLSTAT);

 proc_t proc_info;

 // zero out the allocated proc_info memory
 memset(&proc_info, 0, sizeof(proc_info));

 while (readproc(proc, &proc_info) != NULL) {
  printf("%-10d %-10d ", proc_info.tid, proc_info.ppid);
  if (proc_info.cmdline != NULL) {
   // print full cmd line if available
   printf("%s\n", *proc_info.cmdline);
  } else {
   // if no cmd line use executable filename 
   printf("[%s]\n", proc_info.cmd);
  }
 }

 closeproc(proc);
}

To compile:

$ gcc -o myps myps.c -lproc

The command output. The first column is process ID, the second is the parent process ID, and the third is the process command (if in square brackets the command isn't available and the filename of the executable is shown).

$ ./myps
1          0          /sbin/init
2          0          [kthreadd]
3          2          [ksoftirqd/0]
6          2          [migration/0]
29         2          [cpuset]
30         2          [khelper]
31         2          [netns]
33         2          [sync_supers]

... manually deleted output here so it's not too long

14531      12456      /usr/lib/chromium-browser/chromium-browser --type=renderer --lang=en-GB --force-fieldtest=CacheListSize/CacheListSize_12/ConnCountImpact/conn_count_6/ConnnectBackupJobs/ConnectBackupJobsEnabled/DnsImpact/default_enabled_prefetch/DnsParallelism/parallel_default/GlobalSdch/global_enable_sdch/IdleSktToImpact/idle_timeout_10/Instant/HiddenControlB/Prefetch/ContentPrefetchPrerender1/PrerenderFromOmniboxHeuristic/ConservativeAlgorithm/ProxyConnectionImpact/proxy_connections_32/SpdyCwnd/cwndDynamic/SpdyImpact/npn_with_spdy/WarmSocketImpact/warmest_socket/ --channel=12451.0x7f10f46cde00.1990687626
14557      2          [kworker/7:1]
14562      2          [kworker/3:0]
14574      12901      ./myps

To add more columns, take a look at the proc_t struct in the header file /usr/include/proc/readproc.h.

Converting PHP variables to Javascript variables

Here are some techniques for safely passing PHP variables to Javascript.

Ints and Floats
This one's pretty obvious.

var js_num = <?php echo $php_num; ?>;

Strings
Note that json_encode will take care of the Javascript string quoting delimiters.

var js_str = <?php echo json_encode($php_str); ?>;

Arrays and Associative Arrays
Arrays and associative arrays require that the type first gets encoded to JSON (the first call to json_encode) and then into a string (second call to json_encode) which can be parsed by a Javascript JSON parse function. JSON.parse is included in all recent browsers but to be sure of support use Douglas Crockford's json2.js file which will add it to any browser missing it. jQuery also provides a JSON parsing function.

var js_arr = JSON.parse(<?php echo json_encode(json_encode($php_arr)); ?>);
var js_obj = JSON.parse(<?php echo json_encode(json_encode($php_assoc)); ?>);

Objects
Objects are handled like associative arrays as if get_object_vars had been called upon the object first.