src/minish-once.c

   1 #define _POSIX_C_SOURCE 200809L
   2
   3 #include <errno.h> // EBADF,ENOMEM,errno
   4 #include <limits.h> // CHAR_BIT
   5 #include <locale.h> // LC_ALL,setlocale
   6 #include <stdio.h> // ferror,fputs,getline,perror,ssize_t,stderr,stdin
   7 #include <stdlib.h> // EXIT_FAILURE,NULL,malloc,size_t
   8 #include <unistd.h> // close,execv,write
   9
  10 #define PROGRAM_NAME "minish-once: "
  11
  12 static int write_return(int const fd, int const result) {
  13         if (write(fd, &result, sizeof(result)) == -1) {
  14                 perror(PROGRAM_NAME "write()");
  15                 return EXIT_FAILURE;
  16         }
  17         return result;
  18 }
  19
  20 int main(int argc, char** argv) {
  21         setlocale(LC_ALL, "");
  22         int fd = 0;
  23         if ((size_t)argc < sizeof(fd)) {
  24                 errno = EBADF;
  25                 perror(PROGRAM_NAME "argv");
  26         }
  27         for (size_t i = 0u; i < sizeof(int); ++i) {
  28                 fd |= argv[i + 1u][0] << CHAR_BIT * i;
  29         }
  30         char* line = NULL;
  31         size_t size = 0u;
  32         ssize_t len = getline(&line, &size, stdin);
  33         if (len == -1) {
  34                 if (ferror(stdin)) {
  35                         perror(PROGRAM_NAME "stdin");
  36                         return write_return(fd, EXIT_FAILURE);
  37                 }
  38                 return write_return(fd, 0);
  39         }
  40         if (line[len - 1] == '\n') { // NOTE len cannot be 0
  41                 line[--len] = '\0';
  42         }
  43         size_t words = 1u;
  44         for (char* s = line; s < line + len; ++s) {
  45                 if (!*s) {
  46                         ++words;
  47                 }
  48         }
  49         char** const child_argv = malloc(words * sizeof(char*));
  50         if (!child_argv) {
  51                 errno = ENOMEM;
  52                 perror(PROGRAM_NAME "malloc()");
  53                 return write_return(fd, EXIT_FAILURE);
  54         }
  55         close(fd);
  56         child_argv[0] = line;
  57         size_t i = 1u;
  58         for (char* s = line; s < line + len; ++s) {
  59                 if (!*s) {
  60                         child_argv[i++] = s + 1;
  61                 }
  62         }
  63         child_argv[i] = NULL;
  64         execv(line, child_argv);
  65         int const tmp = errno;
  66         fputs(PROGRAM_NAME, stderr);
  67         errno = tmp;
  68         perror(line);
  69         return EXIT_FAILURE;
  70 }