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/*
* src/command.c
*
* Abstractions for parsing commands from tokens and executing them
* CISC 301 -- Operating Systems, Project 2
*
* Copyright (C) 2025 Douglas B. Rumbaugh <dbrumbaugh@harrisburgu.edu>
*
* Distributed under the Modified BSD License
*
*/
#include "command.h"
#include "config.h"
#include "lexer.h"
#include <stdio.h>
#include <unistd.h>
command *create_command() {
command *cmd = malloc(sizeof(command));
if (!cmd) {
return NULL;
}
cmd->command = NULL;
memset(cmd->args, 0, sizeof(char *));
cmd->pipe[0] = -1;
cmd->pipe[1] = -1;
cmd->infile = NULL;
cmd->outfile = NULL;
cmd->pid = -1;
cmd->next = NULL;
cmd->prev = NULL;
return cmd;
}
command *commands_from_tokens(token *parsed_cmdstr, size_t *cnt) {
command *cmd_head = create_command();
command *cmd = cmd_head;
size_t arg_cnt = 1;
*cnt = 0;
token *prev_tkn = NULL;
for (token *tkn = parsed_cmdstr; tkn; prev_tkn = tkn, tkn = tkn->next) {
if (tkn->type == TKN_COMMAND) {
cmd->command = tkn->text;
cmd->args[0] = tkn->text;
arg_cnt = 1;
(*cnt)++;
} else if (tkn->type == TKN_ARG) {
cmd->args[arg_cnt++] = tkn->text;
} else if (tkn->type == TKN_FILENAME) {
if (prev_tkn->type == TKN_IN_REDIR) {
cmd->infile = tkn->text;
} else {
cmd->outfile = tkn->text;
}
} else if (tkn->type == TKN_PIPE) {
cmd->next = create_command();
cmd->next->prev = cmd;
cmd = cmd->next;
}
}
return cmd_head;
}
void print_commands(FILE *file, command *cmds) {
for (command *cmd = cmds; cmd; cmd = cmd->next) {
fprintf(file, "Command: %s\n", cmd->command);
fprintf(file, "\t");
for (size_t i = 0; i < MAX_ARGUMENT_CNT; i++) {
fprintf(file, "%s ", cmd->args[i]);
}
fprintf(file, "\n\tInfile: %s\n\tOutfile: %s\\n\tPid:%d\n", cmd->infile,
cmd->outfile, cmd->pid);
fprintf(file, "\tRead Pipe: %d\tWrite Pipe: %d\n", cmd->pipe[0],
cmd->pipe[1]);
}
}
void destroy_commands(command *cmds) {
if (!cmds) {
return;
}
command **cmd_ptr = &cmds->next;
while (*cmd_ptr) {
free(cmds);
cmds = *cmd_ptr;
cmd_ptr = &cmds->next;
}
}
pid_t execute_command(command *cmd) {
if (cmd->next && pipe(cmd->pipe) == -1) {
perror("Failed to create pipes");
return -1;
}
pid_t res = fork();
if (res == 0) {
if (cmd->infile && !freopen(cmd->infile, "r", stdin)) {
perror("Could not open input file");
exit(EXIT_FAILURE);
} else if (cmd->prev) {
close(cmd->prev->pipe[1]);
if (dup2(cmd->prev->pipe[0], STDIN_FILENO) == -1) {
perror("Could not assign pipe to stdin");
exit(EXIT_FAILURE);
}
close(cmd->prev->pipe[0]);
}
if (cmd->outfile && !freopen(cmd->outfile, "w", stdout)) {
perror("Could not open output file");
exit(EXIT_FAILURE);
} else if (cmd->next) {
close(cmd->pipe[0]);
if (dup2(cmd->pipe[1], STDOUT_FILENO) == -1) {
perror("Could not assign pipe to stdout");
exit(EXIT_FAILURE);
}
close(cmd->pipe[1]);
}
/*
* NOTE: discarding the const qualifier here is okay because either
* 1) exec fails, in which case the process is aborted immediately
* 2) exec succeeds, in which case the memory is released immediately
*
* In either case, the args won't be accessed again.
*/
execvp(cmd->command, (char **)cmd->args);
perror("Could not run command");
exit(EXIT_FAILURE);
} else if (res < 0) {
perror("Could not run command");
return -1;
}
if (cmd->prev) {
close(cmd->prev->pipe[0]);
close(cmd->prev->pipe[1]);
}
cmd->pid = res;
return res;
}
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