如何以标准的方式修剪前导/尾随空格？
如何以标准的方式修剪前导/尾随空格？
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qq_花开花谢_0
如果可以修改字符串：// Note: This function returns a pointer to a substring of the original string. // If the given string was allocated dynamically, the caller must not overwrite // that pointer with the returned value, since the original pointer must be // deallocated using the same allocator with which it was allocated. The return // value must NOT be deallocated using free() etc.char *trimwhitespace(char *str){ char *end; // Trim leading space while(isspace((unsigned char)*str)) str++; if(*str == 0) // All spaces? return str; // Trim trailing space end = str + strlen(str) - 1; while(end > str && isspace((unsigned char)*end)) end--; // Write new null terminator character end[1] = '\0'; return str;}如果不能修改字符串，则可以使用基本相同的方法：// Stores the trimmed input string into the given output buffer, which must be// large enough to store the result. If it is too small, the output is// truncated.size_t trimwhitespace(char *out, size_t len, const char *str){ if(len == 0) return 0; const char *end; size_t out_size; // Trim leading space while(isspace((unsigned char)*str)) str++; if(*str == 0) // All spaces? { *out = 0; return 1; } // Trim trailing space end = str + strlen(str) - 1; while(end > str && isspace((unsigned char)*end)) end--; end++; // Set output size to minimum of trimmed string length and buffer size minus 1 out_size = (end - str) < len-1 ? (end - str) : len-1; // Copy trimmed string and add null terminator memcpy(out, str, out_size); out[out_size] = 0; return out_size;} -
海绵宝宝撒
这里有一个将字符串转换到缓冲区的第一个位置的方法。您可能需要这种行为，以便如果动态分配字符串，仍然可以在TRIM()返回的指针上释放它：char *trim(char *str){ size_t len = 0; char *frontp = str; char *endp = NULL; if( str == NULL ) { return NULL; } if( str[0] == '\0' ) { return str; } len = strlen(str); endp = str + len; /* Move the front and back pointers to address the first non-whitespace * characters from each end. */ while( isspace((unsigned char) *frontp) ) { ++frontp; } if( endp != frontp ) { while( isspace((unsigned char) *(--endp)) && endp != frontp ) {} } if( str + len - 1 != endp ) *(endp + 1) = '\0'; else if( frontp != str && endp == frontp ) *str = '\0'; /* Shift the string so that it starts at str so that if it's dynamically * allocated, we can still free it on the returned pointer. Note the reuse * of endp to mean the front of the string buffer now. */ endp = str; if( frontp != str ) { while( *frontp ) { *endp++ = *frontp++; } *endp = '\0'; } return str;}检验正确性：int main(int argc, char *argv[]){ char *sample_strings[] = { "nothing to trim", " trim the front", "trim the back ", " trim one char front and back ", " trim one char front", "trim one char back ", " ", " ", "a", "", NULL }; char test_buffer[64]; int index; for( index = 0; sample_strings[index] != NULL; ++index ) { strcpy( test_buffer, sample_strings[index] ); printf("[%s] -> [%s]\n", sample_strings[index], trim(test_buffer)); } /* The test prints the following: [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] [ ] -> [] [ ] -> [] [a] -> [a] [] -> [] */ return 0;}源文件是trim.c。用“cc trim.c-o TRIM”编译。 -
慕码人8056858
我的解决方案。字符串必须是可变的。相对于其他一些解决方案的优点，它将非空格部分移至开头，这样您就可以继续使用旧指针，以防您以后不得不释放()它。void trim(char * s) { char * p = s; int l = strlen(p); while(isspace(p[l - 1])) p[--l] = 0; while(* p && isspace(* p)) ++p, --l; memmove(s, p, l + 1);}此版本创建字符串的副本，而不是在适当的位置进行编辑。strn心得()需要_GNU_source，所以您可能需要使用malloc()和strncpy()创建您自己的strn达普()。char * trim(char * s) { int l = strlen(s); while(isspace(s[l - 1])) --l; while(* s && isspace(* s)) ++s, --l; return strndup(s, l);}
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