Thread: Count the Occurence C Sample

I know this thread is over 5 years old now, but I figured I'd go ahead and post an example.

This program goes a bit above and beyond the initial request in that it scans for all C keywords, rather than just the limited set in the OP. It also uses a slightly more sophisticated method for scanning for keywords. Simply reading text using scanf or fgets and comparing against another string won't necessarily do the trick, since keywords may not be separated by whitespace from other characters (for example, if(x==y), sizeof(int), return(x), etc. These cases would be missed by simple scans. Similarly, we probably don't want to count keywords that appear in text strings, or in comment blocks.

The getIdentifier function below is crude and somewhat ugly, but it scans for identifiers based on the lexical rules given by the C language standard, rather than just by assuming whitespace-delimited strings.

Code:

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

/**
 * Read the next identifier from the stream. 
 *
 * This function is somewhat crude, but it gets the job done.
 * It scans for identifiers based on the following rules, taken 
 * from the C language standard:
 *
 * (6.4.2.1) identifier:
 *             identifier-nondigit
 *             identifier identifier-nondigit
 *             identifier digit
 *
 * (6.4.2.1) identifier-nondigit:
 *             nondigit
 *             universal-character-name
 *             other implementation-defined characters
 *
 * (6.4.2.1) nondigit: one of 
 *             _ a b c d e f g h i j k l m 
 *               n o p q r s t u v w x y z
 *               A B C D E F G H I J K L M 
 *               N O P Q R S T U V W X Y Z
 *
 * (6.4.2.1) digit: one of 
 *               0 1 2 3 4 5 6 7 8 9
 */
char *getIdentifier(FILE *stream, char *buf, size_t bufsize)
{
  size_t i = 0;

  enum {START, PREPROC, STRING, CHAR, SLASH, STAR, LINE_COMMENT, BLOCK_COMMENT, IDENTIFIER} state = START;
  int c;
  int done = 0;

  while (!done && (c = fgetc(stream)) != EOF && i < (bufsize - 1))
  {
    switch(state)
    {
      case START:
        if (c == '_' || isalpha(c))
        {
          buf[i++] = c;
          state = IDENTIFIER;
        }
        else if (c == '/')
          state = SLASH;
        else if (c == '#')
          state = PREPROC;
        else if (c == '"')
          state = STRING;
        else if (c == '\'')
          state = CHAR;
        else if (c == '\\')
          c = fgetc(stream);  /* Throw away the next character */
        break;

      case SLASH:
        if (c == '/')
          state = LINE_COMMENT;
        else if (c == '*')
          state = BLOCK_COMMENT;
        else
          state = START;
        break;

      case LINE_COMMENT:
        if (c == '\n')
          state = START;
        break;

      case BLOCK_COMMENT:
        if (c == '*')
          state = STAR;
        break;

      case STAR:
        if (c == '/')
          state = START;
        else
          state = BLOCK_COMMENT;
        break;

      case PREPROC:
        if (c == '\n')
          state = START;
        break;

      case IDENTIFIER:
        if (c == '_' || isalnum(c))
          buf[i++] = c;
        else
          done=1;
        break;


      case STRING:
        if (c == '\\')
          fgetc(stream); /* Throw away the next character */
        else if (c == '"')
          state = START;
        break;

      case CHAR:
        if (c == '\\')
          fgetc(stream); /* Throw away the next character */
        else if (c == '\'')
          state = START;
        break;

      default:
        break;
    }
  }

  if (c == EOF && i == 0)
    return NULL;
  else
    buf[i] = 0;

  return buf;
}  
  
/**
 * Open the specified file and scan it for keywords. 
 */
int main(int argc, char **argv)
{
  struct keywordEntry {
    char *keyword;
    size_t count;
  };

  FILE *sourceFile;
  char buffer[81]; /* no individual token should be longer than 80 chars */
  size_t total = 0;
  size_t i;

  struct keywordEntry keywordTable[] = {
    {"auto", 0},
    {"break", 0},
    {"case", 0},
    {"char", 0},
    {"const", 0},
    {"continue", 0},
    {"default", 0},
    {"do", 0},
    {"double", 0},
    {"else", 0},
    {"enum", 0},
    {"extern", 0},
    {"float", 0},
    {"for", 0},
    {"goto", 0},
    {"if", 0},
    {"inline", 0}, 
    {"int", 0}, 
    {"long", 0},
    {"register", 0},
    {"restrict", 0},
    {"return", 0},
    {"short", 0},
    {"signed", 0},
    {"sizeof", 0},
    {"static", 0}, 
    {"struct", 0},
    {"switch", 0},
    {"typedef", 0}, 
    {"union", 0}, 
    {"unsigned", 0},
    {"void", 0},
    {"volatile", 0},
    {"while", 0},
    {"_Bool", 0},
    {"_Complex", 0},
    {"_Imaginary", 0},
    {NULL, 0}
  };

  if (argc < 2)
  {
    fprintf(stderr, "USAGE: %s sourcefile\n", argv[0]);
    exit(EXIT_FAILURE);
  }

  sourceFile = fopen(argv[1], "r");
  if (!sourceFile)
  {
     fprintf(stderr, "Could not open file %s\n", argv[1]);
     exit(EXIT_FAILURE);
  }

  /**
   * Read the next identifier from the input stream.
   * If it matches one of the specified keywords, 
   * update that keyword's count.
   */
  while (getIdentifier(sourceFile, buffer, sizeof buffer))
  {
    for (i = 0; keywordTable[i].keyword != NULL; i++)
    {
      if (strcmp(buffer, keywordTable[i].keyword) == 0)
      {
        keywordTable[i].count++;
        total++;
      }
    }
  }
  
  if (ferror(sourceFile))
  {
    fprintf(stderr, "Error while reading %s; aborting\n", argv[1]);
    exit(EXIT_FAILURE);
  }

  fclose(sourceFile);

  printf("%20s%10s\n", "Keyword", "Count");
  printf("%20s%10s\n", "-------", "-----");
  for (i = 0; keywordTable[i].keyword != NULL; i++)
    if (keywordTable[i].count > 0)
      printf("%20s%10d\n", keywordTable[i].keyword, keywordTable[i].count);
  printf("\nTotal: %d\n", total);

  return 0;
}

And here are the results of running the program on its own source text:

Code:

john@marvin:~/projects/keywordCounter$ ./keywordCounter keywordCounter.c 
             Keyword     Count
             -------     -----
               break        10
                case         9
                char         5
             default         1
                else        12
                enum         1
                 for         2
                  if        23
                 int         4
              return         3
              sizeof         1
              struct         2
              switch         1
               while         2

Total: 76