Add write I/O to file

This is a theorical feature listed in http://st.suckless.org/goals. All the
input/output of the terminal will be written to a file, which can be very
useful for debugging, and also allow interconnect st to other process
through named pipes.
---
 st.1 |    6 ++++++
 st.c |   14 +++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

st.1

@@ -10,6 +10,8 @@ st \- simple terminal
 .RB [ \-w 
 .IR windowid ]
 .RB [ \-v ]
+.RB [ \-f
+.IR file ]
 .RB [ \-e
 .IR command ...]
 .SH DESCRIPTION
@@ -30,6 +32,10 @@ embeds st within the window identified by
 .B \-v
 prints version information to stderr, then exits.
 .TP
+.BI \-f " file"
+writes all the I/O to
+.I file
+.TP
 .BI \-e " program " [ " arguments " "... ]"
 st executes
 .I program

st.c

@@ -36,7 +36,7 @@
 
 #define USAGE \
 	"st " VERSION " (c) 2010-2012 st engineers\n" \
-	"usage: st [-t title] [-c class] [-w windowid] [-v] [-e command...]\n"
+	"usage: st [-t title] [-c class] [-w windowid] [-v] [-f file] [-e command...]\n"
 
 /* XEMBED messages */
 #define XEMBED_FOCUS_IN  4
@@ -342,7 +342,9 @@ static STREscape strescseq;
 static int cmdfd;
 static pid_t pid;
 static Selection sel;
+static FILE *fileio;
 static char **opt_cmd  = NULL;
+static char *opt_io    = NULL;
 static char *opt_title = NULL;
 static char *opt_embed = NULL;
 static char *opt_class = NULL;
@@ -776,6 +778,10 @@ ttynew(void) {
 		close(s);
 		cmdfd = m;
 		signal(SIGCHLD, sigchld);
+		if (opt_io && !(fileio = fopen(opt_io, "w"))) {
+			fprintf(stderr, "Error opening %s:%s",
+				opt_io, strerror(errno));
+		}
 	}
 }
 
@@ -1534,6 +1540,9 @@ tputtab(bool forward) {
 void
 tputc(char *c) {
 	char ascii = *c;
+
+	if (fileio)
+		putc(ascii, fileio);
 	if(term.esc & ESC_START) {
 		if(term.esc & ESC_CSI) {
 			csiescseq.buf[csiescseq.len++] = ascii;
@@ -2269,6 +2278,9 @@ main(int argc, char *argv[]) {
 		case 'w':
 			if(++i < argc) opt_embed = argv[i];
 			break;
+		case 'f':
+			if (++i < argc) opt_io = argv[i];
+			break;
 		case 'e':
 			/* eat every remaining arguments */
 			if(++i < argc) opt_cmd = &argv[i];