Socat option -r,-R path specifications allow use of variables

sysutils.c

@@ -941,3 +941,208 @@ double Strtod(const char *nptr, char **endptr, const char *txt) {
    }
    return res;
 }
+
+
+/* This function gets a string with possible references to environment
+   variables and expands them. Variables must be prefixed with '$' and their
+   names consist only of A-Z, a-z, 0-9, and '_'.
+   The name may be enclosed with { }.
+   To pass a literal "$" us "\$".
+   There are special variables supported whose values do not comr from
+   environment:
+   $$ expands to the process's pid
+   $PROGNAME expands to the executables basename or the value of option -lp
+   $TIMESTAMP expands to the actual time in format %Y%m%dT%H%M%S
+   $MICROS expands to the actual microseconds (decimal)
+   The dst output is a copy of src but with the variables expanded.
+   Returns 0 on success;
+   returns -1 when the output buffer was too short (overflow);
+   returns 1 on syntax error.
+*/
+int expandenv(
+	char *dst, 		/* prealloc'd output buff, will be \0 termd */
+	const char *src, 	/* input string to generate expansion from */
+	size_t n, 		/* length of dst */
+	struct timeval *tv) 	/* in/out timestamp for sync */
+{
+	char c; 		/* char currently being lex'd/parsed */
+	bool esc = false;	/* just got '\' */
+	bool bra = false; 	/* within ${ } */
+	char *nam = NULL; 	/* points to temp.allocated rw copy of src */
+	const char *e;		/* pointer to isolated var name in tmp[] */
+	size_t s=0, d=0; 	/* counters in src, dst */
+	size_t v; 		/* variable name begin */
+	bool ofl = false;	/* dst overflow, output truncated */
+	char tmp[18];		/* buffer for timestamp, micros */
+
+	while (c = src[s++]) {
+		if (esc) {
+			if (c == '\0') {
+				if (d+2 > n)  { ofl = true; break; }
+				dst[d++] = '\\';
+				dst[d++] = c;
+				break;
+			}
+			if (c != '$') {
+				if (d+3 > n)  { ofl = true; break; }
+				dst[d++] = '\\';
+			} else {
+				if (d+2 > n)  { ofl = true; break; }
+			}
+			dst[d++] = c;
+			esc = false;
+			continue;
+		}
+		if (c == '\0') {
+			dst[d++] = c;
+			break;
+		}
+		if (c == '\\') {
+			esc = true;
+			continue;
+		}
+		if (c != '$') {
+			if (d+2 > n)  { ofl = true; break; }
+			dst[d++] = c;
+			continue;
+		}
+
+		/* c == '$': Expecting env var to expand */
+		c = src[s];
+		if (c == '\0') {
+			if (d+2 > n)  { ofl = true; break; }
+			++s;
+			dst[d++] = '$';
+			break;
+		}
+		if (c == '$') {
+			int wr;
+			/* Special case: pid */
+			++s;
+			wr = snprintf(&dst[d], n-d, F_pid, getpid());
+			if (wr >= n-d || wr < 0)  { ofl = true; break; }
+			d += wr;
+			continue;
+		}
+		if (c == '{') {
+			++s;
+			bra = true;
+		}
+		if (!isalpha(c) && c != '_') {
+			/* Special case no var name, just keep '$' */
+			if (d+3 > n)  { ofl = true; break; }
+			++s;
+			dst[d++] = '$';
+			dst[d++] = c;
+			continue;
+		}
+		v = 0; 		/* seems we found valid variable name */
+		if (nam == NULL) {
+			nam = strdup(src+s);
+			if (nam == NULL) {
+				errno = ENOMEM;
+				return -1;
+			}
+		}
+		while (c = src[s]) {
+			if (!isalnum(c) && c != '_') {
+				break;
+			}
+			nam[v++] = c;
+			++s;
+		}
+		if (bra && c != '}') {
+			return 1;
+		}
+
+		nam[v] = '\0';
+		/* Var name is complete */
+		/* Check hardcoded var names */
+		if (strcmp(nam, "PROGNAME") == 0) {
+			e = diag_get_string('p');
+		} else if (strcmp(nam, "TIMESTAMP") == 0) {
+			if (tv->tv_sec == 0) {
+				gettimeofday(tv, NULL);
+			}
+			struct tm tm;
+			localtime_r(&tv->tv_sec, &tm);
+			strftime(tmp, sizeof(tmp), "%Y%m%dT%H%M%S", &tm);
+			e = tmp;
+		} else if (strcmp(nam, "MICROS") == 0) {
+			if (tv->tv_sec == 0) {
+				gettimeofday(tv, NULL);
+			}
+			sprintf(tmp, F_tv_usec, tv->tv_usec);
+			e = tmp;
+		} else {
+			e = getenv(nam);
+		}
+		if (e == NULL) {
+			/* Var not found, skip it */
+			continue;
+		}
+		/* Var found, copy it to output buffer */
+		if (d+strlen(e)+1 > n)  { ofl = true; break; }
+		strcpy(&dst[d], e);
+		d += strlen(&dst[d]);
+		continue;
+	}
+
+	if (nam != NULL) {
+		free(nam);
+	}
+
+	if (ofl) {
+		dst[d] = '\0';
+		return -1;
+	}
+	dst[d] = '\0';
+	if (src[s-1] != '\0') {
+		errno = EINVAL;
+		return -1;
+	}
+	return 0;
+}
+
+int xio_opensnifffile(
+	const char *a,
+	struct timeval *tv)
+{
+	char path[PATH_MAX];
+	int flags;
+	int rc;
+	int fd;
+
+	rc = expandenv(path, a, sizeof(path), tv);
+	if (rc < 0) {
+		Error2("expandenv(source=\"%s\", n="F_Zu"): Out of memory", a, sizeof(path));
+		errno = ENOMEM;
+		return -1;
+	} else if (rc > 0) {
+		Error1("expandenv(source=\"%s\"): Syntax error", a);
+		errno = EINVAL;
+		return -1;
+	}
+	flags = O_CREAT|O_WRONLY|O_APPEND|
+#ifdef O_LARGEFILE
+		O_LARGEFILE|
+#endif
+#ifdef O_CLOEXEC
+		O_CLOEXEC|
+#endif
+		O_NONBLOCK;
+	if ((fd = Open(path, flags, 0664)) < 0) {
+		if (errno == ENXIO) {
+			/* try to open pipe rdwr */
+			if ((fd = Open(path, flags, 0664)) < 0) {
+				return -1;
+			}
+		}
+	}
+#ifdef O_CLOEXEC
+	if (Fcntl_l(fd, F_SETFD, FD_CLOEXEC) < 0) {
+		Warn2("fcntl(%d, F_SETFD, FD_CLOEXEC): %s", fd, strerror(errno));
+	}
+#endif
+	return fd;
+}