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");
asked Mar 10, 2011 at 23:05
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);
answered Mar 10, 2011 at 23:07
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@James: casting the return value from
malloc()is not necessary inCand, in fact, is frowned upon because it may hide errors (failure to#include <stdlib.h>).– pmgCommented Mar 10, 2011 at 23:13 -
If I don't typecast in VSC++ I get an error even with stdlib.h included. Commented Mar 10, 2011 at 23:24
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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 aCcompiler!– pmgCommented Mar 10, 2011 at 23:44
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" */
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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, butstrcatdoesn't scale. Commented Mar 10, 2011 at 23:56 -
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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. Commented Mar 11, 2011 at 0:15
'\\'is a backslash, not a slash.