mk_com_readprogf.c

/* read a string from a program's output */
char *mk_com_readprogf(const char *format, ...) {
	static char cmd[32768];
	static char buf[4096];
	static char *out = NULL;
	size_t n = 0, m = 0;
	FILE *fp = (FILE *)0;
	va_list args;

	va_start(args, format);
#if MK_SECLIB
	vsprintf_s(cmd, sizeof(cmd)/2, format, args);
#else
	vsnprintf(cmd, sizeof(cmd)/2, format, args);
	cmd[sizeof(cmd)/2 - 1] = 0;
#endif
	va_end(args);

	if( cmd[0] != '/' ) {
		static char path[sizeof(cmd)/2 - 1];
		size_t repindex;
		char repchar = '\0';
		char *pathvar = NULL;
		
		for( repindex = 0; repindex < sizeof(cmd)-1 && cmd[repindex] != '\0'; ++repindex ) {
			if( cmd[repindex] == ' ' ) {
				if( repindex > 0 && cmd[repindex-1] == '\\' ) {
					continue;
				}

				repchar = cmd[repindex]; // should just be ' ', but we might adjust this
				cmd[repindex] = '\0';
				break;
			}
		}

		if( ( pathvar = getenv("PATH") ) != NULL ) {
			static const char pathenvsep =
#if defined(_WIN32)
				';'
#else
				':'
#endif
				;

			const char *s, *e;
			size_t pathlen;

			s = pathvar;
			do {
				e = strchr( s, pathenvsep );
				if( e != NULL ) {
					pathlen = (size_t)(ptrdiff_t)( e - s );
					mk_com_strncpy( &path[0], sizeof(path)-1, s, pathlen );
					s = e + 1;
				} else {
					mk_com_strcpy( &path[0], sizeof(path)-1, s );
					pathlen = strlen(s);
				}

				if( pathlen > 0 && path[pathlen-1] != '/' && path[pathlen-1] != '\\' ) {
					path[pathlen++] = '/';
					path[pathlen] = '\0';

					++pathlen;
				}

				mk_com_strcpy( &path[pathlen], sizeof(path) - pathlen, cmd );

				if( mk_fs_isFile( path ) ) {
					path[pathlen] = '\0';

					if( repchar != '\0' && repindex < sizeof(cmd) ) {
						cmd[repindex ] = repchar;
						repchar = '\0';
						repindex = ~(size_t)0;
					}
					
					memmove( &cmd[pathlen], &cmd[0], strlen(cmd) + 1 );
					memcpy( &cmd[0], &path[0], pathlen );
					break;
				}
			} while( e != NULL );
		}

		if( repchar != '\0' && repindex < sizeof(cmd) ) {
			cmd[repindex] = repchar;
			repchar = '\0';
			repindex = ~(size_t)0;
		}
	}

#ifdef _WIN32
# undef popen
# undef pclose
# define popen _popen
# define pclose _pclose
#endif
	fp = popen( cmd, "r" );
	if( !fp ) {
		return NULL;
	}

	m = 1024;
	out = (char*)malloc( m );
	if( !out ) {
		abort();
	}

	*out = '\0';
	n = 0;

	while( fgets( buf, sizeof(buf) - 1, fp ) != NULL ) {
		size_t bufn;

		bufn = strlen(buf);
		if( n + bufn + 1 > m ) {
			char *q;

			m += bufn + 1024;
			m += m/2;

			q = realloc( out, m );
			if( !q ) {
				abort();
			}

			out = q;
		}

		memcpy( &out[n], &buf[0], bufn );
		n += bufn;
		out[n] = '\0';
	}

	pclose( fp );
	return out;
}