How can I skip past trailing and leading spaces in C?

Skipping past trailing and leading spaces in C involves iterating through a string and adjusting the start and end pointers to ignore these spaces. Here's how you can do it:

1. Skipping Leading Spaces:

- Iterate through the string from the beginning until you find a non-space character. Update the starting pointer to this position.

2. Skipping Trailing Spaces:

- Iterate through the string from the end until you find a non-space character. Update the ending pointer to this position.

3. Implementation Example:

Here's a C code snippet demonstrating how to skip leading and trailing spaces:

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

void trim(char str) {
  int start = 0;
  int end = strlen(str) - 1;

  // Skip leading spaces
  while (isspace((unsigned char)str[start])) {
    start++;
  }

  // Skip trailing spaces
  while (end >= start && isspace((unsigned char)str[end])) {
    end--;
  }

  // Adjust string to exclude leading and trailing spaces
  int j = 0;
  for (int i = start; i <= end; i++) {
    str[j++] = str[i];
  }
  str[j] = '\\0'; // Null-terminate the trimmed string
}

int main() {
  char str[] = " Hello, World! ";
  printf("Original string: '%s'\\n", str);
  trim(str);
  printf("Trimmed string: '%s'\\n", str);
  return 0;
}

4. Explanation:

- The `trim` function takes a character array (string) as input.

- It initializes `start` to 0 (beginning of the string) and `end` to the last character index.

- It uses `isspace` to check for whitespace characters.

- The first `while` loop increments `start` until a non-space character is found, effectively skipping leading spaces.

- The second `while` loop decrements `end` until a non-space character is found, effectively skipping trailing spaces.

- Finally, it copies the characters from the adjusted `start` to `end` positions into the beginning of the string and null-terminates it.

By using the `isspace` function from `ctype.h`, you ensure that various whitespace characters (space, tab, newline, etc.) are properly handled. Remember to include necessary header files like `stdio.h`, `string.h`, and `ctype.h`. This approach modifies the original string in place.

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