Programming

#include <stdio.h>
#include <regex.h>

int
main ()
{
    regex_t reg;
    char * aaa = "          ";
    
    if (regcomp (&reg, "[^[:space:]$]", REG_EXTENDED|REG_NOSUB) != 0)
        exit(1);
    if ((regexec (&reg, aaa, 0, (regmatch_t *) NULL, 0)) == 0)
         printf ("no match\n");
    else
        printf ("match\n");
    regfree(&reg);
}

void trim_copy(char *input, char *output)
{
  char *end = ouput;
  char c;

  // skip spaces at start
  while(*input && isspace(*input))
    ++input;

  // copy the rest while remembering the last non-whitespace
  while(*input)
  {
    // copy character
    c = *(output++) = *(input++);

    // if its not a whitespace, this *could* be the last character
    if( !isspace(c) )
      end = output;
  }

  // white the terminating zero after last non-whitespace
  *end = 0;
}

void trim_inplace(char *s)
{
  trim_copy(s, s);
 }

char *trim_nocopy(char *s)
{
  char *start = s;

   // skip spaces at start
  while(*start && isspace(*start))
    ++start;

  char *i = start
  // iterate over the rest remebering last non-whitespace
  while(*i)
  {
    if( !isspace(*(i++)) )
      end = i;
  }

  // white the terminating zero after last non-whitespace
  *end = 0;

  return start;
}