string functions?

Is there a function to reverse the order of a string?

strrev

Thank you.

If you have strrev, otherwise you can write your own really easily. This one is independent of any header files, meaning you don't need string.h :-)

Code:

---

#include <stdio.h>

static void revstr(char *s)
{
  char *start;
  char *end;

  /* Find the end */
  for (end = s; *end != '\0'; end++)
  {
    /* Do nothing */
  }

  /* Reverse the string */
  for (start = s, --end; start < end; start++, end--)
  {
    char temp = *start;
    *start = *end;
    *end = temp;
  }
}

int main(void)
{
  char s[] = "A string";

  revstr(s);
  printf("%s\n", s);

  return 0;
}

---

Or you can use strlen and get rid of the first explicit loop :-)

Code:

---

#include <string.h>

static void revstr(char *s)
{
  char *start;
  char *end;

  /* Find the end */
  end = s + (strlen(s) - 1);

  /* Reverse the string */
  for (start = s; start < end; start++, end--)
  {
    char temp = *start;
    *start = *end;
    *end = temp;
  }
}

---

Thank you.

Here's another way of doing it:

Code:

---

#include <stdio.h>

void reverse(char *str)
{
    int i,j=strlen(str)-1;
    for(i=0;i<j;++i,--j)
        str[i] ^= str[j] ^= str[i] ^= str[j];
}


int main()
{
    char *s = "This is a test string.";

    printf("%s\n", s);
    reverse(s);
    printf("%s\n", s);
}

---

Code:

---

/* #include <stdio.h>
    #include <string.h>
*/

void reverse(char *str)
{
    /* strlen returns size_t but at times I use int */
    int i,j=strlen(str)-1;
    for(i=0;i<j;++i,--j)
                /*  http://www.eskimo.com/~scs/C-faq/q3.8.html */
        str[i] ^= str[j] ^= str[i] ^= str[j];
}


int main()
{
    /* On some machines stores the string in read only memory */
    char *s = "This is a test string.";

    printf("%s\n", s);
    reverse(s);
    printf("%s\n", s);

    /* main returns an integer value */
    /* return 0; */
}

---