Pipes not working while implementing a minishell - c

Question

I'm actually trying to implement a basic minishell in C. For doing that, I made a fonction which parse what the user enter in the console. I parsed it and then I would like to send the command to the console using pipes. I don't understand why my pipes are not working.
I checked the parsing and it seems to be fine, i have the right commands in parameters of the fonction.
The thing is that my pipe code is literally doing nothing and I don't understand why.
Here is my code.
Thank you in advance.
#define READ 0
#define WRITE 1
char *cmds[5] = {0};
int main() {
char *saisie = (char*)malloc(100*sizeof(char*));
char *saisie2 = (char*)malloc(100*sizeof(char*));
gets(saisie);
int ncmds = 0;
int k = 0;
char* token = (char*)malloc(100*sizeof(char*));
char* tofree;
if(*(saisie + 0) == '$'){
if(*(saisie + 2) == 'e' && *(saisie + 3) == 'x' && *(saisie + 4) == 'i' || *(saisie + 5) == 't'){
exit(0);
}
else{
int i;
for(i = 0;i<99;i++){
*(saisie2+i) = *(saisie+i+1);
}
free(saisie);
if (saisie2 != NULL) {
tofree = saisie2;
while ((token = strsep(&saisie2, "|")) != NULL){
cmds[ncmds] = token;
ncmds++;
}
free(tofree);
}
}
}
exe(cmds, ncmds);
while(wait(NULL) > 0);
return 0;
}
int exe(char *cmds[], int ncmds){
int fdin, fdout;
int fds[2];
int i;
int status;
fdin = 0;
for(i=0; i < ncmds-1; i++){
pipe(fds);
fdout = fds[WRITE];
if(fork() == 0){
if( fdin != 0 ) {
close(0);
dup(fdin);
close(fdin);
}
if( fdout != 1 ) {
close(1);
dup(fdout);
close(fdout);
}
close(fds[READ]);
const char* prog2[] = {cmds[i], "-l", 0};
execvp(cmds[i], prog2);
fprintf(stderr, "si esto se ve es un error\n");
exit(1);
}
if(fdin != 0)
close(fdin);
if(fdout != 1)
close(fdout);
fdin = fds[READ];
}
/* Ultimo comando */
fdout = 1;
if(fork() == 0) {
if( fdin != 0 ) {
close(0);
dup(fdin);
close(fdin);
}
const char* prog2[] = {cmds[i], "-l", 0};
execvp(cmds[i], prog2);
close(fds[READ]);
exit(1);
}
if(fdout!= 1)
close(fdout);
if(fdin != 0)
close(fdin);
}
}

Answer 1

int exe(char *cmds[], int ncmds){
int p2c[2];//pipe parent to child
int c2p[2];//pipe child to parent
int i;
int status;
int pid;
char buf[4096];
memset(buf, 0, 4096);
for(i=0; i < ncmds; i++){
pipe(p2c);
pipe(c2p);
pid = fork();
if(pid < 0) {
exit 1;
}
if(pid == 0){ //in child
close(1);
dup2(c2p[1],1); // make child write to c2p pipe instead of stdout
close(0);
dup2(p2c[0],0); // make child read from p2c pipe instead of stdin
close(p2c[1]);
close(c2p[0]);
const char* prog2[] = {cmds[i], "-l", 0};
execvp(cmds[i], prog2);
fprintf(stderr, "si esto se ve es un error\n");
exit(1);
}
//in parent
write(p2c[1], buf, strlen(buf)); //write the last output to child
close(p2c[1]);
close(c2p[1]);
memset(buf,0,4096);
if(read(c2p[0], buf, 4096) > 0){ //read output from child
if(i == ncmds -1 ){
printf("result:\n");
printf("%s\n", buf);
}
}
}
}