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POCreate a filename with basepath + extension and current date in C [char *array]
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copied!<p>I'm a totally newbie in C but I want to create a string (not C++ string) with a basepath, current date and time and a given extension. I saw this topic: <a href="https://stackoverflow.com/questions/5138913/c-putting-current-date-in-a-filename">C - putting current date in a filename</a> and created my simple code:</p> <pre><code>#include <stdio.h> #include <stdlib.h> #include <string.h> #include <time.h> char* currdatetime() { const int size = 20; char *cdt = (char*)malloc(sizeof(char)*size); if(cdt == NULL) { return NULL; } memset (cdt, 0, size); time_t currDateTime; currDateTime = time(NULL); if(currDateTime == -1) { return NULL; } struct tm *timeinfo = localtime (&currDateTime); if(strftime(cdt, 20, "%d.%m.%y_%H:%M:%S", timeinfo) == 0) { return NULL; } cdt[size] = '\0'; return cdt; } char *getname(const char *pathtofile, const char *ext) { char *timestamp = currdatetime(); int size = (strlen(pathtofile) + strlen(ext) + strlen(timestamp) + 1); char *filename = (char*)malloc(sizeof(char)*size); if(filename == NULL) { return NULL; } memset (filename, 0, size); strcpy(filename, pathtofile); strcpy(filename+strlen(pathtofile), timestamp); strcpy(filename+strlen(pathtofile)+strlen(timestamp), ext); filename[size] = '\0'; return filename; } int main(void) { printf("\n\n%s\n\n", getname("file_", ".txt")); printf("\n\n%s\n\n", getname("file_", ".html")); return(0); } </code></pre> <p>But the output is like this:</p> <pre><code>file_06.08.13_13:06:47.txt *** glibc detected *** ./test: free(): invalid pointer: 0x092f6020 *** ======= Backtrace: ========= /lib/i386-linux-gnu/libc.so.6(+0x75ee2)[0xb7630ee2] /lib/i386-linux-gnu/libc.so.6(+0xa96f9)[0xb76646f9] /lib/i386-linux-gnu/libc.so.6(+0xa99f2)[0xb76649f2] /lib/i386-linux-gnu/libc.so.6(localtime+0x2d)[0xb766311d] ./test[0x8048572] ./test[0x80485be] ./test[0x804874a] /lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf3)[0xb75d44d3] ./test[0x8048471] ======= Memory map: ======== 08048000-08049000 r-xp 00000000 08:07 663115 /home/ivy/Desktop/CTests/test 08049000-0804a000 r--p 00000000 08:07 663115 /home/ivy/Desktop/CTests/test 0804a000-0804b000 rw-p 00001000 08:07 663115 /home/ivy/Desktop/CTests/test 092f6000-09317000 rw-p 00000000 00:00 0 [heap] b757f000-b759b000 r-xp 00000000 08:05 656309 /lib/i386-linux-gnu/libgcc_s.so.1 b759b000-b759c000 r--p 0001b000 08:05 656309 /lib/i386-linux-gnu/libgcc_s.so.1 b759c000-b759d000 rw-p 0001c000 08:05 656309 /lib/i386-linux-gnu/libgcc_s.so.1 b75ba000-b75bb000 rw-p 00000000 00:00 0 b75bb000-b775e000 r-xp 00000000 08:05 655398 /lib/i386-linux-gnu/libc-2.15.so b775e000-b7760000 r--p 001a3000 08:05 655398 /lib/i386-linux-gnu/libc-2.15.so b7760000-b7761000 rw-p 001a5000 08:05 655398 /lib/i386-linux-gnu/libc-2.15.so b7761000-b7764000 rw-p 00000000 00:00 0 b777f000-b7783000 rw-p 00000000 00:00 0 b7783000-b7784000 r-xp 00000000 00:00 0 [vdso] b7784000-b77a4000 r-xp 00000000 08:05 659665 /lib/i386-linux-gnu/ld-2.15.so b77a4000-b77a5000 r--p 0001f000 08:05 659665 /lib/i386-linux-gnu/ld-2.15.so b77a5000-b77a6000 rw-p 00020000 08:05 659665 /lib/i386-linux-gnu/ld-2.15.so bfefc000-bff1d000 rw-p 00000000 00:00 0 [stack] Przerwane (core dumped) file_06.08.13_13:06:47.txt *** glibc detected *** ./test: free(): invalid pointer: 0x092f6020 *** ======= Backtrace: ========= /lib/i386-linux-gnu/libc.so.6(+0x75ee2)[0xb7630ee2] /lib/i386-linux-gnu/libc.so.6(+0xa96f9)[0xb76646f9] /lib/i386-linux-gnu/libc.so.6(+0xa99f2)[0xb76649f2] /lib/i386-linux-gnu/libc.so.6(localtime+0x2d)[0xb766311d] ./test[0x8048572] ./test[0x80485be] ./test[0x804874a] /lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf3)[0xb75d44d3] ./test[0x8048471] ======= Memory map: ======== 08048000-08049000 r-xp 00000000 08:07 663115 /home/ivy/Desktop/CTests/test 08049000-0804a000 r--p 00000000 08:07 663115 /home/ivy/Desktop/CTests/test 0804a000-0804b000 rw-p 00001000 08:07 663115 /home/ivy/Desktop/CTests/test 092f6000-09317000 rw-p 00000000 00:00 0 [heap] b757f000-b759b000 r-xp 00000000 08:05 656309 /lib/i386-linux-gnu/libgcc_s.so.1 b759b000-b759c000 r--p 0001b000 08:05 656309 /lib/i386-linux-gnu/libgcc_s.so.1 b759c000-b759d000 rw-p 0001c000 08:05 656309 /lib/i386-linux-gnu/libgcc_s.so.1 b75ba000-b75bb000 rw-p 00000000 00:00 0 b75bb000-b775e000 r-xp 00000000 08:05 655398 /lib/i386-linux-gnu/libc-2.15.so b775e000-b7760000 r--p 001a3000 08:05 655398 /lib/i386-linux-gnu/libc-2.15.so b7760000-b7761000 rw-p 001a5000 08:05 655398 /lib/i386-linux-gnu/libc-2.15.so b7761000-b7764000 rw-p 00000000 00:00 0 b777f000-b7783000 rw-p 00000000 00:00 0 b7783000-b7784000 r-xp 00000000 00:00 0 [vdso] b7784000-b77a4000 r-xp 00000000 08:05 659665 /lib/i386-linux-gnu/ld-2.15.so b77a4000-b77a5000 r--p 0001f000 08:05 659665 /lib/i386-linux-gnu/ld-2.15.so b77a5000-b77a6000 rw-p 00020000 08:05 659665 /lib/i386-linux-gnu/ld-2.15.so bfefc000-bff1d000 rw-p 00000000 00:00 0 [stack] (core dumped) </code></pre> <p>And I dont really know what is wrong and how to fix this ...</p> <p><strong>OK, added this, result is the same:</strong></p> <pre><code>char *f1 = getname("file_", ".txt"); char *f2 = getname("file_", ".html"); printf("\n\n%s\n\n", f1); printf("\n\n%s\n\n", f2); free(f1); free(f2); </code></pre> <p><strong>CODE THAT FINALLY WORKED:</strong></p> <pre><code>#include <stdio.h> #include <stdlib.h> #include <string.h> #include <time.h> char* currdatetime() { const int size = 20; char *cdt = (char*)malloc(sizeof(char)*size); if(cdt == NULL) { return NULL; } memset (cdt, 0, size); time_t currDateTime; currDateTime = time(NULL); if(currDateTime == -1) { return NULL; } struct tm *timeinfo = localtime (&currDateTime); if(strftime(cdt, 20, "%d.%m.%y_%H:%M:%S", timeinfo) == 0) { return NULL; } return cdt; } char *getname(const char *pathtofile, const char *ext) { char *timestamp = currdatetime(); int size = (strlen(pathtofile) + strlen(ext) + strlen(timestamp) + 1); char *filename = (char*)malloc(sizeof(char)*size); if(filename == NULL) { return NULL; } memset (filename, 0, size); strcpy(filename, pathtofile); strcpy(filename+strlen(pathtofile), timestamp); strcpy(filename+strlen(pathtofile)+strlen(timestamp), ext); free(timestamp); timestamp = NULL; return filename; } int main(void) { char *f1 = getname("file_", ".txt"); char *f2 = getname("file_", ".html"); printf("\n\n%s\n\n", f1); printf("\n\n%s\n\n", f2); free(f1); free(f2); return(0); } </code></pre>

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