Hello.

I'm making my shell in c and I want to use linux command as external command.

Below is my code and it work well. If I put "cat file.txt" it work. but if I put "cat -n file.txt", it doesn't work.

Please give help, tell me specifically

#include #include #include #include #include #include #include #include #include

#define BUF_SIZE 1024 #define READ 0 #define WRITE 1

char** eliminateToken(char **token, int size, int pos1, int pos2);

int main(int argc, char **argv) { char *buffer = malloc(sizeof(char) * BUF_SIZE); char **token = malloc(sizeof(char*) * BUF_SIZE); int c, status, position, fd; pid_t pid;

do { position = 0; printf("$ "); while (true) { c = getchar();

if (c == EOF || c == ' ') { buffer[position] = '\0'; break; } else { buffer[position] = c; } position++; } token[0] = strtok(buffer, " "); for(position = 1; position < BUF_SIZE; position++) { token[position] = strtok(NULL, " "); if (token[position] == NULL) { break; } } token = realloc(token, sizeof(char*) * position);

pid = fork(); if (pid < 0) { perror("fork error"); exit(EXIT_FAILURE); } else if (pid == 0) { for (int i = 0; i < position; i++) { if (!strncmp(token[i], ">>", 2)) { if ((fd = open(token[i+1], O_RDWR | O_APPEND | O_CREAT, 0666)) < 0) { perror("open error"); close(fd); exit(EXIT_FAILURE); } dup2(fd, WRITE); token = eliminateToken(token, position, i, i+1); break; } else if (!strncmp(token[i], ">", 1)) { if ((fd = open(token[i+1], O_RDWR | O_TRUNC | O_CREAT, 0666)) < 0) { perror("open error"); close(fd); exit(EXIT_FAILURE); } dup2(fd, WRITE); token = eliminateToken(token, position, i, i+1); break; } } if (execvp(token[0], token) == -1) { perror("exec error"); exit(EXIT_FAILURE); } close(fd); } else { waitpid(pid, &status, WUNTRACED); }

puts(""); token = calloc(position, sizeof(char*) * BUF_SIZE); } while (!status);

free(buffer); free(token); return EXIT_SUCCESS; }

char** eliminateToken(char **token, int size, int pos1, int pos2) { char **eliminate_buffer = malloc(sizeof(char*) * BUF_SIZE); int position = 0;

for (int i = 0; i < size; i++) { if (i != pos1 && i != pos2) { eliminate_buffer[position] = token[i]; position++; } }

return eliminate_buffer; }