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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3.  
  4. char *trim(char *str)
  5. {
  6.     size_t len = 0;
  7.     char *frontp = str;
  8.     char *endp = NULL;
  9.  
  10.     if( str == NULL ) { return NULL; }
  11.     if( str[0] == '\0' ) { return str; }
  12.  
  13.     len = strlen(str);
  14.     endp = str + len;
  15.  
  16.     /* Move the front and back pointers to address the first non-whitespace
  17.      * characters from each end.
  18.      */
  19.     while( isspace((unsigned char) *frontp) ) { ++frontp; }
  20.     if( endp != frontp )
  21.     {
  22.         while( isspace((unsigned char) *(--endp)) && endp != frontp ) {}
  23.     }
  24.  
  25.     if( str + len - 1 != endp )
  26.             *(endp + 1) = '\0';
  27.     else if( frontp != str &&  endp == frontp )
  28.             *str = '\0';
  29.  
  30.     /* Shift the string so that it starts at str so that if it's dynamically
  31.      * allocated, we can still free it on the returned pointer.  Note the reuse
  32.      * of endp to mean the front of the string buffer now.
  33.      */
  34.     endp = str;
  35.     if( frontp != str )
  36.     {
  37.             while( *frontp ) { *endp++ = *frontp++; }
  38.             *endp = '\0';
  39.     }
  40.  
  41.  
  42.     return str;
  43. }
  44.  
  45. int main(int argc, char *argv[])
  46. {
  47.     char *sample_strings[] =
  48.     {
  49.             "nothing to trim",
  50.             "    trim the front",
  51.             "trim the back     ",
  52.             " trim one char front and back ",
  53.             " trim one char front",
  54.             "trim one char back ",
  55.             "                   ",
  56.             " ",
  57.             "\n\n\nNewlines in the front",
  58.             "Newlines in the back\n\n\n",
  59.             "\nOne newline in front",
  60.             "One newline in back\n",
  61.             "\n\n\n\n\n\n\n\n\n",
  62.             "\n",
  63.             "a",
  64.             "",
  65.             NULL
  66.     };
  67.     char test_buffer[64];
  68.     int index;
  69.  
  70.     for( index = 0; sample_strings[index] != NULL; ++index )
  71.     {
  72.             strcpy( test_buffer, sample_strings[index] );
  73.             printf("[%s] -> [%s]\n", sample_strings[index],
  74.                                      trim(test_buffer));
  75.     }
  76.  
  77.     /* The test prints the following:
  78.     [nothing to trim] -> [nothing to trim]
  79.     [    trim the front] -> [trim the front]
  80.     [trim the back     ] -> [trim the back]
  81.     [ trim one char front and back ] -> [trim one char front and back]
  82.     [ trim one char front] -> [trim one char front]
  83.     [trim one char back ] -> [trim one char back]
  84.     [                   ] -> []
  85.     [ ] -> []
  86.     [a] -> [a]
  87.     [] -> []
  88.     */
  89.  
  90.     return 0;
  91. }
Success #stdin #stdout 0s 2168KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
[nothing to trim] -> [nothing to trim]
[    trim the front] -> [trim the front]
[trim the back     ] -> [trim the back]
[ trim one char front and back ] -> [trim one char front and back]
[ trim one char front] -> [trim one char front]
[trim one char back ] -> [trim one char back]
[                   ] -> []
[ ] -> []
[


Newlines in the front] -> [Newlines in the front]
[Newlines in the back


] -> [Newlines in the back]
[
One newline in front] -> [One newline in front]
[One newline in back
] -> [One newline in back]
[








] -> []
[
] -> []
[a] -> [a]
[] -> []
https://ideone.com/bbVmqo
language:
C (gcc 8.3)
created:
7 years ago
visibility:
public

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