[tips] using pyrex to do the argv[0] trick in linux using python.

A trick to rename python process in output of 'top' and 'ps'.

set_argv.c:

#include 
#include 
#include 

int get_argc(){
    int argc;
    char **argv;
    Py_GetArgcArgv(&argc, &argv);
    return argc;
}

void set_argv_via_number(int num,char *str){
    int argc;
    char **argv;
    Py_GetArgcArgv(&argc, &argv);
    strncpy(argv[num], str , strlen(str));
    memset(&argv[num][strlen(str)], '\0', strlen(&argv[num][strlen(str)]));
}


set_processname.pyx:

#Warning: this module is not safe and may involve some dirty hacks.
import sys,dl,glob
cdef extern int get_argc()
cdef extern void set_argv_via_number(int num,char *buf)
def set_argv0(thename):
    set_argv_via_number(0,thename)

def set_argv(thename):
    argc = get_argc()
    print argc
    for i in xrange(argc+1):
        if i==0:
            set_argv0(thename)
        else:
            pass
def set_name(thename):
    if sys.platform == 'linux2':
        # Set process name.  Only works on Linux >= 2.1.57.
        try:
            libc_loc = glob.glob("/lib/libc.so*")[0]
            libc = dl.open(libc_loc)
            libc.call('prctl', 15, thename, 0, 0, 0) # 15 is PR_SET_NAME
        except:
            pass    

def set_processname(thename):
    space_padding_num = len(sys.argv[0])-len(thename)
    if space_padding_num < 0:
        #thename is longer than original name
        newname = thename[:len(sys.argv[0])]
    else:
        #thename is shorter. add padding.
        newname = thename + " " * space_padding_num

    set_name(newname)
    set_argv(newname)

compile.sh:
#!/bin/sh
CC=mipsel-linux-gcc

pyrexc set_processname.pyx
$CC -c -fPIC -I/usr/include/python2.5/ set_argv.c
$CC -c -fPIC -I/usr/include/python2.5/ set_processname.c
$CC -shared set_argv.o set_processname.o -o set_processname.so