bexec is a binary-safe replacement for exec.
samoc: This is a work-around for exec being broken for binary input/output. -- See http://tip.tcl.tk/259.html
proc bexec {command input} {
# Execute shell "command", send "input" to stdin, return stdout.
# Ignores stderr (but "2>@1" can be part of "command").
# Supports binary input and output. e.g.:
# set flac_data [bexec {flac -} $wav_data]
# Run "command" in background...
set f [open |$command {RDWR BINARY}]
fconfigure $f -blocking 0
# Connect read function to collect "command" output...
set ::bexec_done.$f 0
set ::bexec_output.$f {}
fileevent $f readable [list bexec_read $f]
# Send "input" to command...
puts -nonewline $f $input
unset input
close $f write
# Wait for read function to signal "done"...
vwait ::bexec_done.$f
# Retrieve output...
set result [set ::bexec_output.$f]
unset ::bexec_output.$f
unset ::bexec_done.$f
fconfigure $f -blocking 1
close $f
return $result
}
proc bexec_read {f} {
# Accumulate output in ::bexec_output.$f.
append ::bexec_output.$f [read $f]
if {[eof $f]} {
fileevent $f readable {}
set ::bexec_done.$f 1
}
}The following fails with "channel "rc0" does not support OS handles" (AMG mentions this on the exec page).
set in [tcl::chan::variable input] chan configure $in -translation binary -blocking 0 exec $command <@$in
The patch below enables:
encoding system iso8859-1 set flac [exec -binarystdout flac --totally-silent - << $wav]
Setting the system encoding to iso8859-1 (AKA "binary") causes the $wav string to be treated as binary (encoding system says "The system encoding is used whenever Tcl passes strings to system calls")
The -binarystdout option asks exec to configure its internal output channel as "-translation binary".
A downside here is that << causes exec to call mkstemps() and write the $wav string into a temporary file. exec really should be fixed so that a large string in RAM can be sent to the stdin pipe without intermediate buffering or temporary files. (Note I think the puts call in proc bexec does something like: copy $input to a buffer; set up a "writeable" event handler; write from buffer to pipe inside vwait.)
diff -u -r tcl8.6.1/generic/tclIOCmd.c tcl8.6.1.patched/generic/tclIOCmd.c
--- tcl8.6.1/generic/tclIOCmd.c 2013-09-20 05:04:14.000000000 +1000
+++ tcl8.6.1.patched/generic/tclIOCmd.c 2014-05-21 00:00:32.000000000 +1000
@@ -877,12 +877,12 @@
const char *string;
Tcl_Channel chan;
int argc, background, i, index, keepNewline, result, skip, length;
- int ignoreStderr;
+ int ignoreStderr, binaryStdout;
static const char *const options[] = {
- "-ignorestderr", "-keepnewline", "--", NULL
+ "-ignorestderr", "-keepnewline", "-binarystdout", "--", NULL
};
enum options {
- EXEC_IGNORESTDERR, EXEC_KEEPNEWLINE, EXEC_LAST
+ EXEC_IGNORESTDERR, EXEC_KEEPNEWLINE, EXEC_BINARYSTDOUT, EXEC_LAST
};
/*
@@ -891,6 +891,7 @@
keepNewline = 0;
ignoreStderr = 0;
+ binaryStdout = 0;
for (skip = 1; skip < objc; skip++) {
string = TclGetString(objv[skip]);
if (string[0] != '-') {
@@ -904,6 +905,8 @@
keepNewline = 1;
} else if (index == EXEC_IGNORESTDERR) {
ignoreStderr = 1;
+ } else if (index == EXEC_BINARYSTDOUT) {
+ binaryStdout = 1;
} else {
skip++;
break;
@@ -955,6 +958,10 @@
return TCL_ERROR;
}
+ if (binaryStdout) {
+ Tcl_SetChannelOption(interp, chan, "-translation", "binary");
+ }
+
if (background) {
/*
* Store the list of PIDs from the pipeline in interp's result and
@@ -1002,7 +1009,7 @@
* newline character.
*/
- if (keepNewline == 0) {
+ if (keepNewline == 0 && binaryStdout == 0) {
string = TclGetStringFromObj(resultPtr, &length);
if ((length > 0) && (string[length - 1] == '\n')) {
Tcl_SetObjLength(resultPtr, length - 1);Below is an alternate patch that dispenses with the -binarystdout option. Instead it looks at what the system encoding is set to. If it is set to binary then exec output is treated as binary.
diff -u -r tcl8.6.1/generic/tclIOCmd.c tcl8.6.1.patched/generic/tclIOCmd.c
--- tcl8.6.1/generic/tclIOCmd.c 2013-09-20 05:04:14.000000000 +1000
+++ tcl8.6.1.patched/generic/tclIOCmd.c 2014-05-21 00:16:29.000000000 +1000
@@ -877,7 +877,7 @@
const char *string;
Tcl_Channel chan;
int argc, background, i, index, keepNewline, result, skip, length;
- int ignoreStderr;
+ int ignoreStderr, binaryStdout;
static const char *const options[] = {
"-ignorestderr", "-keepnewline", "--", NULL
};
@@ -955,6 +955,11 @@
return TCL_ERROR;
}
+ binaryStdout = (strcmp(Tcl_GetEncodingName(NULL), "iso8859-1") == 0);
+ if (binaryStdout) {
+ Tcl_SetChannelOption(interp, chan, "-translation", "binary");
+ }
+
if (background) {
/*
* Store the list of PIDs from the pipeline in interp's result and
@@ -1002,7 +1007,7 @@
* newline character.
*/
- if (keepNewline == 0) {
+ if (keepNewline == 0 && binaryStdout == 0) {
string = TclGetStringFromObj(resultPtr, &length);
if ((length > 0) && (string[length - 1] == '\n')) {
Tcl_SetObjLength(resultPtr, length - 1);