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pipes.cpp
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115 lines (100 loc) · 2.45 KB
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//PANAGIOTIS KONTOEIDIS
//1115201900266
#include "libs.h"
void pipes(tokens cmd1, tokens cmd2) //opens a pipe between two commands
{
int fd[2];
pid_t pid;
int s1 = cmd1.size();
int s2 = cmd2.size();
char **par1 = new char *[s1 + 1];
char **par2 = new char *[s2 + 1];
for (int i = 0; i < s1; i++)
{ // cmd 1
par1[i] = cmd1[i];
}
par1[s1] = nullptr;
for (int i = 0; i < s2; i++)
{ // cmd 2
par2[i] = cmd2[i];
}
par2[s2] = nullptr;
if (pipe(fd) == -1) // call pipe
{
perror(" pipe ");
exit(1);
}
if ((pid = fork()) == -1) // lecture 9 p.53
{
perror(" fork ");
exit(1);
}
if (pid == 0)
{ // child and writer
close(fd[0]);
dup2(fd[1], STDOUT_FILENO);
close(fd[1]);
execvp(par1[0], par1);
perror(" execlp ");
exit(-1);
}
else
{ // parent and reader
close(fd[1]);
dup2(fd[0], STDIN_FILENO);
close(fd[0]);
execvp(par2[0], par2);
exit(-1);
}
}
void check_for_pipes(tokens command) // turns on pipe flag if pipe symbol found
{
int pipe_pos = -1;
for (int i = 0; i < command.size(); i++)
{ // find pipe symbol position to split the command into two commands
if (strcmp(command[i], "|") == 0)
{
pipe_flag++;
return;
}
}
return;
}
void call_for_pipes(tokens command) // splits command to two sub commands to pass to pipes()
{
int pipe_pos = -1;
tokens cmd1;
tokens cmd2;
for (int i = 0; i < command.size(); i++) // find pipe symbol position to split the command into two commands
{
if (strcmp(command[i], "|") == 0)
{
pipe_pos = i;
break;
}
}
if (redirection_flag == 0) // if we have no redirections
{
for (int i = 0; i < pipe_pos; i++)
{ // cmd1
cmd1.push_back(command[i]);
}
for (int i = pipe_pos + 1; i < command.size(); i++)
{ // cmd2
cmd2.push_back(command[i]);
}
}
else
{
int k = rpos.front(); // get first redirection symbol position to run the command
for (int i = 0; i < pipe_pos; i++)
{ // cmd1
cmd1.push_back(command[i]);
}
for (int i = pipe_pos + 1; i < k; i++)
{ // cmd2
cmd2.push_back(command[i]);
}
}
pipes(cmd1, cmd2);
}