在下面的代码,我不调用malloc。
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
/* Change this to '\\' if you are doing this on MS-windows or something like it. */
#define DIR_SYM '/'
#define EXT_SYM '.'
#define NEW_EXT "jpg"
int main(int argc, char * argv[]) {
char * fname;
char * outdir;
if (argc < 3) {
fprintf(stderr, "I want more command line arguments\n");
return 1;
}
fname = argv[1];
outdir = argv[2];
char * fname_base_begin = strrchr(fname, DIR_SYM); /* last occurrence of DIR_SYM */
if (!fname_base_begin) {
fname_base_begin = fname; // No directory symbol means that there's nothing
// to chop off of the front.
}
char * fname_base_end = strrchr(fname_base_begin, EXT_SYM);
/* NOTE: No need to search for EXT_SYM in part of the fname that we have cut off
* the front and then have to deal with finding the last EXT_SYM before the last
* DIR_SYM */
if (!fname_base_end) {
fprintf(stderr, "I don't know what you want to do when there is no extension\n");
return 1;
}
*fname_base_end = '\0'; /* Makes this an end of string instead of EXT_SYM */
/* NOTE: In this code I actually changed the string passed in with the previous
* line. This is often not what you want to do, but in this case it should be ok.
*/
// This line should get you the results I think you were trying for in your example
printf("string=%s%c%s_test%c%s\n", outdir, DIR_SYM, fname_base_begin, EXT_SYM, NEW_EXT);
// This line should just append _test before the extension, but leave the extension
// as it was before.
printf("string=%s%c%s_test%c%s\n", outdir, DIR_SYM, fname_base_begin, EXT_SYM, fname_base_end+1);
return 0;
}
我能够与不分配内存建在字符串中,因为我让printf
其实担心构建它脱身,并采取知道原来FNAME串不会在将来需要的优势。
我可以计算多长时间将需要基于各部分,然后用sprintf
形成对我来说是字符串已分配的字符串的空间。
另外,如果你不想改变fname
字符串的内容你也可以使用了:
printf("string=%s%c%*s_test%c%s\n", outdir, DIR_SYM, (unsigned)fname_base_begin -(unsigned)fname_base_end, fname_base_begin, EXT_SYM, fname_base_end+1);
为了printf
只使用字符串的一部分。
+1,但我认为你的意思是“空字符”,而不是“空指针”。 – 2010-08-24 18:47:09
@David X:谢谢!修正了。 – 2010-08-24 20:45:25