Hello,
I seem to be having trouble with pipe and select.
Context: Have to program something which will be shell executed as such:
logn [--tick n] cmd [args] [, cmd [args]]...
Basically, it's a program that multiple programs simultanously.
Constraints: Each output line has to start with it's command number in front in format printf "%d: %s"
ie:
0: first line of first command.
0: second line of first command.
1: first line of second command.
0: third line of first command.
1: second line of second command.
If the tick has been specified, system will print a period if no output has been sent for n seconds. Must use Select() If the last output was a period, system does not print another period.
Issues:
1) It seems the output of the second command goes to the p[0] of the first pipe.
When I read into p[0][0] i get what was sent to p[1][0]. there doesn't seem to be anything in p[1][0].
2) Whenever my select encouters a timeout, it seems to get stuck there.
I asked a question earlier, so it may seems familiar. As the issue was different, I made a new post. The old post helped me alot to figure out the forking.
Here's my code:
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/time.h>
#include "readline.h"
/* Fetches the number of commands in parameters. Number of Commas + 1 */
int getNbCmd(char ** argv)
{
int nbCmd = 1;
int i = 0;
while(argv[i] != '\0')
{
if(strcmp(argv[i], ",") == 0)
nbCmd++;
i++;
}
return nbCmd;
}
/* Fills the Command Array */
void getCommandes(char *** tbCmd, int argc, char ** argv)
{
int indexArgv = 1;
int indexCmd = 0;
int indexTbCmd = 0;
char ** cmd = (char **)malloc(argc*sizeof(char *));
if(indexArgv < argc)
{
if(strcmp(argv[indexArgv], "--tick") == 0)
indexArgv = 3;
}
while (indexArgv < argc)
{
if(strcmp(argv[indexArgv], ",") == 0)
{
cmd[indexCmd] = (char *) 0;
tbCmd[indexTbCmd] = cmd;
free(cmd);
cmd = (char **)malloc(argc*sizeof(char *));
indexTbCmd++;
indexCmd = 0;
}
else
{
char * arg;
arg = argv[indexArgv];
cmd[indexCmd] = arg;
indexCmd++;
}
indexArgv++;
}
cmd[indexCmd] = (char *) 0;
tbCmd[indexTbCmd] = cmd;
free(cmd);
}
int main (int argc, char ** argv)
{
int nbCmds = getNbCmd(argv);
int tick = -1;
char *** tbCmd = (char ***) malloc (nbCmds*sizeof(char **));
if(argc > 3)
{
if(strcmp(argv[1], "--tick") == 0)
tick = atoi(argv[2]);
}
getCommandes(tbCmd, argc, argv);
int i,j;
pid_t pidM[nbCmds];
int p[nbCmds][2];
for (i = 0;i < nbCmds;i++)
{
if ( pipe( p[i] ) != 0 ){ perror( "pipe()" ); exit(1); }
}
for (i = 0;i < nbCmds;i++)
{
// fork() to get child process
pidM[i] = fork();
if ( pidM[i] < 0 ){ perror( "fork()" ); exit(1); }
//Child Processing
else if (pidM[i] == 0)
{
close(p[i][0]);
dup2(p[i][1], STDOUT_FILENO);
int ret;
ret = execvp(tbCmd[i][0], tbCmd[i]);
perror("execvp()");
}
}
// Parent Processing
for (i = 0;i < nbCmds;i++)
{
close(p[i][1]);
}
char * buffer;
int retval = 1;
int boolAfficher = 0;
int nbNull = 0;
fd_set set;
struct timeval timeout;
/* Initialize the file descriptor set. */
FD_ZERO (&set);
for (i = 0;i < nbCmds;i++)
{
FD_SET (p[i][0], &set);
}
while(nbNull < nbCmds)
{
if(tick >= 0)
{
timeout.tv_sec = (unsigned int)tick;
timeout.tv_usec = 0;
retval = select (FD_SETSIZE,&set, NULL, NULL, &timeout);
}
else
retval = select (FD_SETSIZE,&set, NULL, NULL, NULL);
if(retval == 0)
{
if(boolAfficher == 0 && tick >= 0)
{
printf(".\n");
boolAfficher = 1;
}
}
else if(retval > 0)
{
for (i = 0;i < nbCmds;i++)
{
if(FD_ISSET(p[i][0], &set))
{
buffer = readline(p[i][0]);
if(buffer[0] != '\0')
{
printf("%d: %s", i, buffer);
}
else
{
FD_CLR(p[i][0], &set);
nbNull++;
}
}
else
printf("Not ISSET[%d]\n", i);
free(buffer);
}
}
else
perror("select()");
}
wait(NULL);
free(tbCmd);
exit(0);
}