README

Task

This program implements a simple version of a command pipeline using fork and pipe system calls. The program creates two child processes to execute two different commands and redirects their input and output through a pipe. The main function:

How to build and run the program

Build it using:

git clone git@github.com:JohannaGcd/42_pipex.git && cd 42_pipex && make

Run it with:

 ./pipex infile "ls -l" "wc -l" outfile

Should behave as:

< infile ls -l | wc -l > outfile

What I Learned

1. Process Management:

   • Forking Processes: Using fork() to create child processes and managing process IDs.
   • Waiting for Processes: Using waitpid() to wait for child processes to finish and get their exit statuses.

2. Inter-Process Communication (IPC):

   • Pipes: Using pipe() to create a pipe for communication between processes and dup2() to redirect standard input and output.

3. File Descriptors and Redirection:

   • File Operations: Using open() to open files and handle file descriptors.
   • Redirection: Redirecting input and output streams using dup2().

4. Error Handling:

   • Error Reporting: Using perror() to report errors and handle them gracefully.

5. Command Execution:

   • Executing Commands: Using execve() to execute commands within child processes.
   • Retrieving Command Paths: Determining executable paths using environment variables (PATH) and handling command execution errors.

6. Memory Management:

   • Dynamic Memory: Allocating and freeing memory for command arguments and paths using functions like ft_split() and free().

Functions

• main(): Initializes pipes and processes, forks two child processes, and waits for their completion.
• execute_child(): Prepares and executes commands in child processes, handling input/output redirection and command execution.
• open_file(): Opens input or output files based on the child process.
• redirect_fds(): Redirects file descriptors for input and output.
• close_pipes(): Closes unused pipe file descriptors.
• set_in_and_out(): Sets up input and output redirection for child processes.
• retrieve_cmds(): Retrieves the full path of commands to be executed.
• retrieve_env_path(): Retrieves the PATH environment variable.
• get_cmd(): Splits a command string into arguments.
• get_env_path(): Retrieves the value of the PATH environment variable.
• get_cmd_path(): Constructs the full path for an executable command.