Programming

#include <stdio.h> 
#include <stdlib.h> 
#include <sys/types.h> 
#include <sys/wait.h> 
#include <string.h> 
#include <signal.h> 
#include <errno.h> 
#include <setjmp.h> 
#define MAX_EPRG_ARGS   10 
#define MAX_LEN   5000 
#define EXT_PRG_TIMEOUT   30 /* Seconds */ 
/* For signal processing */ 
pid_t pid_to_kill   = (-1); 
jmp_buf env; 
void sig_alrm (int dummy) 
{ 
if (pid_to_kill>0) 
  { 
   kill (pid_to_kill,9); /* Kill it */ 
   longjmp (env,1); 
  } 
} 
int execute (char * ext_prg, 
char * ext_arg, 
char * ext_output, 
size_t bufsize) 
{ 
  int rcode = -1; 
  int Pipe [2]; 
  int status = 0; 
  char * ARGUMENTS [MAX_EPRG_ARGS]; 
  char temp_str [5000]; 
  int i=0; 
  int ret_wpd = -1; 
  char data [2]; 
  sig_t prev; 
  /* Clear the buffer */ 
  memset (ext_output,0,bufsize); 
  prev=signal (SIGALRM,sig_alrm); 
  if (setjmp(env)!=0) 
  { 
   /* Here returns longjmp */ 
   if (pid_to_kill>0) 
   { 
    /* Return the prev sigaction */ 
    signal (SIGALRM,prev); 
    snprintf (temp_str,sizeof(temp_str)-1,"execute(): Timeout waiting external program termination, killing pid: %lu",pid_to_kill); 
    write_log (temp_str); 
    close (Pipe[0]); 
    close (Pipe[1]); 
    return (-1); 
   } 
  } 
  if (pipe(Pipe)==-1) 
   { 
    snprintf (temp_str,sizeof(temp_str)-1,"execute(): Cannot create pipe: '%s' !\n",strerror(errno)); 
    write_log (temp_str); 
    return (-1); 
   } 

  memset (&temp_str,0,sizeof(temp_str)); 
  if ((rcode=fork ())==0)  /* Child */ 
   { 
    for (i=0;i<=MAX_EPRG_ARGS-1;i++) ARGUMENTS[i]=NULL; 
    ARGUMENTS[0]=ext_prg; 
    ARGUMENTS[1]=strtok (ext_arg, " \t");     
    if (ARGUMENTS[1]!=NULL) 
     { 
       for (i=2;i<=MAX_EPRG_ARGS-1;i++) 
        { 
         ARGUMENTS[i]=strtok (NULL, " \t");     
         if (ARGUMENTS[i]==NULL) break; 
        } 
     } 
    /* First close the read end of the pipe */ 
    close (Pipe[0]);     
    /* Make a dup */ 
    if (dup2(Pipe[1],1)==-1) 
     { 
      snprintf (temp_str,sizeof(temp_str)-1,"execute(): 'Dup2' command failed: '%s' !\n",strerror(errno)); 
      write_log (temp_str); 
      close (Pipe[0]); 
      close (Pipe[1]); 
      exit (253); 
     } 
     
    if (execv(ext_prg,ARGUMENTS)==-1) 
     { 
      snprintf (temp_str,sizeof(temp_str)-1,"execute(): Cannot execute external programm: '%s', Error: '%s' !\n",ext_prg,strerror(errno)); 
      write_log (temp_str); 
      close (Pipe[0]); 
      close (Pipe[1]); 
      exit (253); /* Parent will get return status: 253 */ 
     } 
    close (Pipe[1]); 
   } 
   
  if (rcode==-1)  /* Parent */ 
   { 
    snprintf  (temp_str,sizeof(temp_str)-1,"execute(): 'Fork' command failed: '%s' !\n",strerror(errno)); 
    write_log (temp_str); 
    close (Pipe[0]); 
    close (Pipe[1]); 
    return -1; 
   } 
  /* Prepare for signal processing */ 
  pid_to_kill=rcode; 
   
  alarm (EXT_PRG_TIMEOUT); 

  if (waitpid (rcode,&status, (WUNTRACED))==-1) 
   { 
    snprintf (temp_str,sizeof(temp_str)-1,"execute(): 'Waitpid' command failed: '%s' !\n",strerror(errno)); 
    write_log (temp_str); 
    close (Pipe[0]); 
    close (Pipe[1]); 
    return -1; 
   } 

  /* First close the write end of the pipe */ 
  close (Pipe[1]);     
  memset (&data,0,sizeof(data)); 
  while (read(Pipe[0],data,1)>0) 
  { 
   if (strlen(ext_output)<(bufsize-1)) strcat (ext_output,data); 
   memset (&data,0,sizeof(data)); 
  } 
  alarm (0); /* Stop the timer */ 
   
  signal (SIGALRM,prev); /* Return the prev sigaction */ 
  if (WIFEXITED(status)) 
   { 
    rcode=WEXITSTATUS (status); 
    if (rcode==253) goto L1; 
    else 
    { 
     close (Pipe[0]); 
     return (rcode); 
    } 
   } 
L1: 
  snprintf (temp_str,sizeof(temp_str)-1,"execute(): Abnormal child termination !\n"); 
  write_log (temp_str); 
  close (Pipe[0]); 
  close (Pipe[1]); 
  return -1; 
}