I have a line like the one below, but I need to concat slashes for directories, is there any way to safely concat multiple strings?
// Need to include \\ after windowsDir
FILE *dest = fopen(strcat(windowsDir, filename),"wb");
2 Answers
char *buf = malloc(strlen(windowsDir) + 1 + strlen(filename) + 1); // len + \ + len + \0
sprintf(buf, "%s\\%s", windowsDir, filename);
FILE *dest = fopen(buf, "wb");
free(buf);
7 Comments
James Guvna Redmond
forgot the typecast before malloc.
pmg
@James: casting the return value from
malloc() is not necessary in C and, in fact, is frowned upon because it may hide errors (failure to #include <stdlib.h>).James Guvna Redmond
If I don't typecast in VSC++ I get an error even with stdlib.h included.
pmg
I'm pretty sure you can configure the Microsoft compiler to be a C89 compiler. I don't use it though, so I can't help you with the proper way to set it up. If you're writing
C, use a C compiler! |
Supposing there is enough space all around, this works
strcpy(buff, "C:\\foobar");
strcpy(value, "file.txt");
strcat(strcat(buff, "\\"), value);
/* buff now has "C:\\foobar\\file.txt" */
3 Comments
Jim Balter
I would note that
sprintf (or better, snprintf) is more general, more precise, and doesn't have to rescan the previous string for every append ... not a problem here, but strcat doesn't scale.Jim Balter
Oops ... s/precise/concise/ .... It's particularly bad when it's the library designer who is the schlemiel. strcat never ever should have been in the library, and strcpy should have been spec'ed to return a ptr to the NUL, not to the beginning of the string. The best solution at this point is to abandon this C language abomination, and yet we see one C homework question after another here.
'\\'is a backslash, not a slash.