Question

我是C语言的新手，并且一直致力于一个程序，它接受一个文本文件或来自键盘的输入，并将所有字母转换为大写字母，小写字母，或根据输入将它们旋转13个位置由用户给出的应该是：./ tconv -u test.txt 理论上，这应该将test.txt中的所有字母都转换为大写字母。如果没有给出文件，。/ tconv -u，那么它应该从键盘输入。

我认为我遗漏了一些相当简单的东西，但是当我用任何-r，-u或-l参数运行它时，它说它无法读取＆＃34; -r＆＃34;，＆＃34; - 你＆＃34;，或＆＃34; -l＆＃34;。我错过了什么？

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>

FILE*
input_from_args(int argc, const char *argv[])
{
  if (argc==1){
    return stdin;
  }else{
    return fopen(argv[1],"r");
  }
}

int
rot13(c)
{
  int e;
  int ROT;
  ROT = 13;
  if(c>='A' && c <='Z'){
    if((e=c+ROT)<='Z')
      return e;
    else{
      e = c - ROT;
      return e;
    }
  }
  else{
    return c;
  }
}

int
main(int argc, const char*argv[])
{
  FILE *src = input_from_args(argc,argv);
  FILE *dest = stdout;
  if (src == NULL){
    fprintf(stderr, "%s: unable to open %s\n", argv[0], argv[1]);
    exit(EXIT_FAILURE);
  }
  char *rotate = "-r";
  char *lower = "-l";
  char *upper = "-u";
  int i;
  i =0;
  int ch;
while ((ch = fgetc(src))!=EOF){
    if (strcmp(upper,argv[i])==0){
      fprintf(dest,"%c",toupper(ch));
    }
    else if (strcmp(lower,argv[i])==0){
      fprintf(dest,"%c",tolower(ch));
    }
    else if (strcmp(rotate,argv[i])==0){
      fprintf(dest,"%c",rot13(ch));
    }
    else{
      fprintf(dest,"%c",ch);
    }
  }
  fclose(src);
  return EXIT_SUCCESS;
}

Answer 1

Argv [0]是你的程序，argv [1]是你的标志，argv [2]是你提供的文件名。您正在尝试打开名为“-r”的文件argv [1]

Answer 2

如果您使用的是Linux平台，可以查看getopt_long来解析命令行选项。它由GNU提供，适用于Linux系统，并且取决于系统。对于系统无关的命令行解析Google gflags

这将有助于减少命令行解析的开销，您可以更专注于程序逻辑。

以下是http://www.gnu.org/software/libc/manual/html_node/Getopt-Long-Option-Example.html

的示例

#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>

/* Flag set by ‘--verbose’. */
static int verbose_flag;

int
main (int argc, char **argv)
{
  int c;

  while (1)
    {
      static struct option long_options[] =
        {
          /* These options set a flag. */
          {"verbose", no_argument,       &verbose_flag, 1},
          {"brief",   no_argument,       &verbose_flag, 0},
          /* These options don’t set a flag.
             We distinguish them by their indices. */
          {"add",     no_argument,       0, 'a'},
          {"append",  no_argument,       0, 'b'},
          {"delete",  required_argument, 0, 'd'},
          {"create",  required_argument, 0, 'c'},
          {"file",    required_argument, 0, 'f'},
          {0, 0, 0, 0}
        };
      /* getopt_long stores the option index here. */
      int option_index = 0;

      c = getopt_long (argc, argv, "abc:d:f:",
                       long_options, &option_index);

      /* Detect the end of the options. */
      if (c == -1)
        break;

      switch (c)
        {
        case 0:
          /* If this option set a flag, do nothing else now. */
          if (long_options[option_index].flag != 0)
            break;
          printf ("option %s", long_options[option_index].name);
          if (optarg)
            printf (" with arg %s", optarg);
          printf ("\n");
          break;

        case 'a':
          puts ("option -a\n");
          break;

        case 'b':
          puts ("option -b\n");
          break;

        case 'c':
          printf ("option -c with value `%s'\n", optarg);
          break;

        case 'd':
          printf ("option -d with value `%s'\n", optarg);
          break;

        case 'f':
          printf ("option -f with value `%s'\n", optarg);
          break;

        case '?':
          /* getopt_long already printed an error message. */
          break;

        default:
          abort ();
        }
    }

  /* Instead of reporting ‘--verbose’
     and ‘--brief’ as they are encountered,
     we report the final status resulting from them. */
  if (verbose_flag)
    puts ("verbose flag is set");

  /* Print any remaining command line arguments (not options). */
  if (optind < argc)
    {
      printf ("non-option ARGV-elements: ");
      while (optind < argc)
        printf ("%s ", argv[optind++]);
      putchar ('\n');
    }

  exit (0);
}

C文本转换程序

2 个答案: