How do I save the cursor position into a variable in TCL ?
The best I can come up with is:
set tty [open /dev/tty w]
puts $tty "\033\[6n"
close $tty
set position [read stdin]
puts $position
but I cannot capture the output.
I have also tried using ::term::ansi::send::qcp from Tcllib but get the same problem.
(FYI I tried to model the above TCL on a PHP answer from How to get cursor position with PHP-CLI?).
It's tricky to get this right, as we need to read a partial line and it's not yielded by the terminal implementation immediately. After experimenting a bit, the most reliable approach that I found was this:
proc readbits {{chan stdin}} {
set s ""
while {![eof $chan]} {
set c [read $chan 1]
append s $c
if {$c eq "R"} break
}
return $s
}
proc getcur {} {
puts -nonewline "\u001b\[6n"
flush stdout
scan [readbits] "\u001b\[%d;%dR"
}
# Must be in raw+noecho mode for this to work!
exec stty raw -echo
puts [getcur]
# Restore normal mode
exec stty -raw echo
In Tcl 8.7, you can use: fconfigure stdin -mode raw and fconfigure stdin -mode normal in place of those exec stty calls.
Related
Hi I am using this piece of code for inserting pipe in TCL. Can anybody please let me understand when this condition [gets $pipe line] >= 0 fails.
For eg: only when [gets $pipe line] is a negative number this will fail.
In my case it is never returning a negative number and the TestEngine hangs forever
set pipeline [open "|Certify.exe filename" "r+"]
fileevent $pipeline readable [list handlePipeReadable $pipeline]
fconfigure $pipeline -blocking 0
proc handlePipeReadable {pipe} {
if {[gets $pipe line] >= 0} {
# Managed to actually read a line; stored in $line now
} elseif {[eof $pipe]} {
# Pipeline was closed; get exit code, etc.
if {[catch {close $pipe} msg opt]} {
set exitinfo [dict get $opt -errorcode]
} else {
# Successful termination
set exitinfo ""
}
# Stop the waiting in [vwait], below
set ::donepipe $pipe
} else {
puts ""
# Partial read; things will be properly buffered up for now...
}
}
vwait ::donepipe
The gets command (when given a variable to receive the line) returns a negative number when it is in a minor error condition. There are two such conditions:
When the channel has reached end-of-file. After the gets the eof command (applied to the channel) will report a true value in this case.
When the channel is blocked, i.e., when it has some bytes but not a complete line (Tcl has internal buffering to handle this; you can get the number of pending bytes with chan pending). You only see this when the channel is in non-blocking mode (because otherwise the gets will wait indefinitely). In this case, the fblocked command (applied to the channel) will return true.
Major error conditions (such as the channel being closed) result in Tcl errors.
If the other command only produces partial output or does something weird with buffering, you can get an eternally blocked pipeline. It's more likely with a bidirectional pipe, such as you're using, as the Certify command is probably waiting for you to close the other end. Can you use it read-only? There are many complexities to interacting correctly with a process bidirectionally! (For example, you probably want to make the pipe's output buffering mode be unbuffered, fconfigure $pipeline -buffering none.)
Please find the way the certify process is being triggered from the command prompt and the print statements are given just for the understanding. At the end the process hangs and the control is not transferred back to the TCL
From the documentation for gets:
If varName is specified and an empty string is returned in varName because of end-of-file or because of insufficient data in nonblocking mode, then the return count is -1.
Your script is working completely fine. checked with set pipeline [open "|du /usr" "r+"]
instead of your pipe and included puts "Line: $line" to check the result. So its clear that there is some problem in Certify command. Can you share your command, how do you use on terminal and how did you use with exec?
################### edited by Drektz
set pipeline [open "|du /usr" "r+"]
fileevent $pipeline readable [list handlePipeReadable $pipeline]
fconfigure $pipeline -blocking 0
proc handlePipeReadable {pipe} {
if {[gets $pipe line] >= 0} {
# Managed to actually read a line; stored in $line now
################### included by Drektz
puts "Line: $line"
} elseif {[eof $pipe]} {
# Pipeline was closed; get exit code, etc.
if {[catch {close $pipe} msg opt]} {
set exitinfo [dict get $opt -errorcode]
} else {
# Successful termination
set exitinfo ""
}
# Stop the waiting in [vwait], below
set ::donepipe $pipe
} else {
puts ""
# Partial read; things will be properly buffered up for now...
}
}
vwait ::donepipe
you can see it in the CMDwith& screenshot mentioned.Is there any workaround that I have to overcome the issue
Please see the issue when run with the help of exec executable args &
EDIT: Original example and alternative solution framework modified for clarity.
The line buffering behaviour might behave differently than expected in Tcl 8.6. The following code blocks without any output, unless the "chan close" line is uncommented:
set data {one two four}
set stream [open |[list cat -n] r+]
chan configure $stream -buffering line
chan puts $stream "$data\n"
chan puts $stream "\n"
chan flush $stream
#chan close $stream write
set out [chan read $stream]
puts "output: $out"
chan close $stream
So this simplistic solution does not work for interactive I/O, and this might be related to synchronization problems at both ends of the pipe.
Using a channel event structure (e.g., based on http://www.beedub.com/book/2nd/event.doc.html), seems to be preferable:
proc chanReader { pipe } {
global extState
while 1 {
set len [chan gets $pipe line]
if { $len > 0 } {
puts "<< $line."
continue
} else {
if { [chan blocked $pipe] } {
set extState 1
return
} elseif { [chan eof $pipe] } {
set extState 2
return
}
}
}
}
set data {one two foure}
set timeout 5000
#set stream [open [list | cat -n] r+]
#set stream [open [list | ispell -a] r+]
set stream [open [list | tr a-z A-Z] r+]
#set stream [open [list | fmt -] r+]
chan configure $stream -blocking 0 -buffering line
set extState 0
chan event $stream readable [list chanReader $stream]
foreach word $data {
puts "> $word\n"
chan puts $stream "$word\n"
chan flush $stream
#chan close $stream write
set aID [after $timeout {set extState 3}]
vwait extState
if { $extState == 1 } {
# Got regular output.
after cancel $aID
puts "Cancel $aID."
continue
} elseif { $extState == 2 } {
puts "External program closed."
chan close $stream
exit 2
} elseif { $extState == 3 } {
puts "Timeout."
chan close $stream
exit 3
}
}
puts "End of task."
chan close $stream
exit 0
This code fragment works with the "cat -n" and "ispell -a" external programs (commented lines), but still fails with other external programs. For instance it does not work with the "tr a-z A-Z" and "fmt" examples above.
If the line "chan close $stream write" above is uncommented, we receive output from the external program, but this terminates the interaction with it. How to reliably connect (interactively) to these external programs?
I'm guessing that the core issue here is that there's two sources of buffering going on, and Tcl only has control over one of them. But both stem from the fact that virtually all output, when not going to an “interactive” destination (i.e., a terminal), is buffered. There's basically a call in the C standard library that determines this and enables the buffering feature, and Tcl follows that rule too (despite using its entirely independent I/O library). Doing this massively speeds up non-interactive pipeline processing, but means that if you're expecting to see every byte output exactly at the point when the program thinks it is writing it, you're going to be disappointed.
Of course, programs can switch this buffering off if they want. In Tcl, this is done by fconfigure $channel -buffering none (or line for line-oriented buffering). In cat, the -n option makes it do the equivalent (calling setvbuf() in C) and ispell is probably doing the same. But most programs don't. Some instead call fflush() from time to time; that works too, but is also a minority practice. So with a bidirectional pipeline such as you're using, you can easily force the side where you feed into it from Tcl not buffer, but you can't usually get the other side to do the same.
There is a workaround: run the subprocess with Expect. That puts a fake terminal between Tcl and the subprocess (instead of a pipe) and tricks it into thinking it is talking direct to the user. But the consequence of this is that you have to substantially rewrite your Tcl program and you gain a dependency on a (very fine!) external package.
# Prints the string in a file
puts $chan stderr "$timestamp - Running test: $test"
# Prints the string on a console
puts "$timestamp - Running test: $test"
Is there a way I can send the output of puts to the screen and to a log file at the same time? Currently I have both the above two lines one after the other in my script to achieve this.
Or is there any other solution in tcl ?
Use the following proc instead of puts:
proc multiputs {args} {
if { [llength $args] == 0 } {
error "Usage: multiputs ?channel ...? string"
} elseif { [llength $args] == 1 } {
set channels stdout
} else {
set channels [lrange $args 0 end-1]
}
set str [lindex $args end]
foreach ch $channels {
puts $ch $str
}
}
Examples:
# print on stdout only
multiputs "1"
# print on stderr only
multiputs stderr "2"
set brieflog [open brief.log w]
set fulllog [open detailed.log w]
# print on stdout and in the log files
multiputs stdout $brieflog $fulllog "3"
This isn't something I've used extensively, but it seems to work (Tcl 8.6+ only):
You need the channel transform tcl::transform::observe package:
package require tcl::transform::observe
Open a log file for writing and set buffering to none:
set f [open log.txt w]
chan configure $f -buffering none
Register stdout as a receiver:
set c [::tcl::transform::observe $f stdout {}]
Anything written to the channel $c will now go to both the log file and stdout.
puts $c foobar
Note that it would seem to make more sense to have the channel transformation on top of stdout, with the channel to the log file as receiver, but I haven't been able to make that work.
Documentation:
chan,
open,
package,
puts,
set,
tcl::transform::observe (package)
Currently I am firing following command
set pid [exec make &]
set term_id [wait pid]
First command will execute makefile inside TCL and Second Command will wait for first command's makefile operation to complete. First command displays all logs of makefile on stdout. Is it possible to store all logs in variable or file when "&" is given in the last argument of exec using redirection or any other method?
If "&" is not given then we can take the output using,
set log [exec make]
But if "&" is given then command will return process id,
set pid [exec make &]
So is it possible stop the stdout logs and put them in variable?
If you are using Tcl 8.6, you can capture the output using:
lassign [chan pipe] reader writer
set pid [exec make >#$writer &]
close $writer
Don't forget to read from the $reader or the subprocess will stall. Be aware that when used in this way, the output will be delivered fully-buffered, though this is more important when doing interactive work. If you want the output echoed to standard out as well, you will need to make your script do that. Here's a simple reader handler.
while {[gets $reader line] >= 0} {
lappend log $line
puts $line
}
close $reader
Before Tcl 8.6, your best bet would be to create a subprocess command pipeline:
set reader [open |make]
If you need the PID, this can become a bit more complicated:
set reader [open |[list /bin/sh -c {echo $$; exec make}]]
set pid [gets $reader]
Yes, that's pretty ugly…
[EDIT]: You're using Tk, in Tcl 8.5 (so you need the open |… pipeline form from above), and so you want to keep the event loop going. That's fine. That's exactly what fileevent is for, but you have to think asynchronously.
# This code assumes that you've opened the pipeline already
fileevent $reader readable [list ReadALine $reader]
proc ReadALine {channel} {
if {[gets $channel line] >= 0} {
HandleLine $line
} else {
# No line could be read; must be at the end
close $channel
}
}
proc HandleLine {line} {
global log
lappend log $line; # Or insert it into the GUI or whatever
puts $line
}
This example does not use non-blocking I/O. That might cause an issue, but probably won't. If it does cause a problem, use this:
fconfigure $reader -blocking 0
fileevent $reader readable [list ReadALine $reader]
proc ReadALine {channel} {
if {[gets $channel line] >= 0} {
HandleLine $line
} elseif {[eof $channel]} {
close $channel
}
}
proc HandleLine {line} {
global log
lappend log $line
puts $line
}
More complex and versatile versions are possible, but they're only really necessary once you're dealing with untrusted channels (e.g., public server sockets).
If you'd been using 8.6, you could have used coroutines to make this code look more similar to the straight-line code I used earlier, but they're a feature that is strictly 8.6 (and later, once we do later versions) only as they depend on the stack-free execution engine.
I have a file contain lines with path to the files. Sometimes a path contain SHELL environment variable and I want to check the file existence.
The following is my solution:
set fh [open "the_file_contain_path" "r"]
while {![eof $fh]} {
set line [gets $fh]
if {[regexp -- {\$\S+} $line]} {
catch {exec /usr/local/bin/tcsh -c "echo $line" } line
if {![file exists $line]} {
puts "ERROR: the file $line is not exists"
}
}
}
I sure there is more elegant solution without using
/usr/local/bin/tcsh -c
You can capture the variable name in the regexp command and do a lookup in Tcl's global env array. Also, your use of eof as the while condition means your loop will interate one time too many (see http://phaseit.net/claird/comp.lang.tcl/fmm.html#eof)
set fh [open "the_file_contain_path" "r"]
while {[gets $fh line] != -1} {
# this can handle "$FOO/bar/$BAZ"
if {[string first {$} $line] != -1} {
regsub -all {(\$)(\w+)} $line {\1::env(\2)} new
set line [subst -nocommand -nobackslashes $new]
}
if {![file exists $line]} {
puts "ERROR: the file $line does not exist"
}
}
First off, it's usually easier (for small files, say of no more than 1–2MB) to read in the whole file and split it into lines instead of using gets and eof in a while loop. (The split command is very fast.)
Secondly, to do the replacement you need the place in the string to replace, so you use regexp -indices. That does mean that you need to take a little more complex approach to doing the replacement, with string range and string replace to do some of the work. Assuming you're using Tcl 8.5…
set fh [open "the_file_contain_path" "r"]
foreach line [split [read $fh] "\n"] {
# Find a replacement while there are any to do
while {[regexp -indices {\$(\w+)} $line matchRange nameRange]} {
# Get what to replace with (without any errors, just like tcsh)
set replacement {}
catch {set replacement $::env([string range $line {*}$nameRange])}
# Do the replacement
set line [string replace $line {*}$matchRange $replacement]
}
# Your test on the result
if {![file exists $line]} {
puts "ERROR: the file $line is not exists"
}
}
TCL programs can read environment variables using the built-in global variable env. Read the line, look for $ followed by a name, look up $::env($name), and substitute it for the variable.
Using the shell for this is very bad if the file is supplied by untrusted users. What if they put ; rm * in the file? And if you're going to use a shell, you should at least use sh or bash, not tcsh.