Want to use some custom function (written in tcl) in Unix pipeline ie grep patt file.rpt | tclsh summary.tcl. How to make tcl script to take output from the pipeline, process and out on the commandline as if a normal unix command?
This is very easy! The script should read input from stdin (probably with gets) and write output to stdout (with puts; this is the default destination).
Here's a very simple by-line filter script:
set lineCount 0
while {[gets stdin line] >= 0} {
incr lineCount
puts stdout "$lineCount >> $line <<"
}
puts "Processed $lineCount lines in total"
You probably want to do something more sophisticated!
The gets command has two ways of working. The most useful one here is the one where it takes two arguments (channel name, variable name), writes the line it has read from the channel into the variable, and returns the number of characters read or -1 when it has an EOF (or would block in non-blocking mode, or has certain kinds of problems; you can ignore these cases). That works very well with the style of working described above in the sample script. (You can distinguish the non-success cases with eof stdin and fblocked stdin, but don't need to for this use case.)
Related
I am trying to run a tcl script through .bat file. I want to read some cmd arguments in the tcl script. Below is my code:
Command to run:
D:\Cadence\Sigrity2021.1\tools\bin\PowerSI.exe -tcl abcd.tcl %new_var%.spd %new_file_name%
Below is how I am trying to read the variable in the tcl file:
sigrity::open document [lindex $argv 0] {!}
It open up the Cadence Sigrity, but I see the below error:
How do I read cmd argument in tcl?
If you have no other way to do it that you can find (and it sounds like that might be the case) then you can fake it by writing a helper file with content like this, filling in the real arguments in the appropriate places:
# Name of script to call
set ::argv0 "abcd.tcl"
# Arguments to pass
set ::argv {}
lappend ::argv "%new_var%.spd"
lappend ::argv "%new_file_name%"
# Number of arguments (rarely used)
set ::argc [llength $::argv]
# Do the call
source $::argv0
Then you can pass that file to PowerSI and it will set things up and chain to the real file. It's messy, but practical.
If you're writing this from Tcl, use the list command to do the quoting of the strings (instead of putting them in double quotes) as it will do exactly the right thing for you. If you're writing the file from another language, you'll want to make sure you put backslashes in before \, ", $ and [ characters. The fiddlyness of doing that depends on your language.
I'm not a Tcl programmer, but I need to modify a Tcl script that invokes an external command and tries to separate stdout and stderr. The following is a minimal example of how the script currently does this.
#!/usr/bin/tclsh8.4
set pipe [open "|cmd" r]
while {[gets $pipe line] >= 0} {puts $line}
catch "close $pipe" errorMsg
puts "$errorMsg"
Here, cmd is a an external command, and for the sake of this example, I will replace it with the following shell script. (I'm working on a Linux machine, but you can modify this to write to stdout and stderr however is appropriate for your system.)
#!/bin/sh -f
echo "A" > /dev/stdout
echo "B" > /dev/stdout
echo "C" > /dev/stderr
echo "D" > /dev/stderr
When I execute cmd, I get the following four lines as expected:
% ./cmd
A
B
C
D
However, when I execute my Tcl script, I get:
% ./test.tcl
A
B
D
This is an example of a more general phenomenon, which is that catch seems to swallow all but the last line of stderr.
To me, the "obvious" way to approach this is to try to mimic what is happening with stdout, which obviously works and prints all lines of the output. However, the current implementation is based on getting a Tcl channel by using open "|cmd", which requires running an external command. I can't figure out how to create a channel without opening an external command, and even if I could figure that out, there are subsequent issues with this approach. (How do I get the output of close into the channel? And if I need to open a new channel to get the output of each channel I am closing, then wouldn't I need an infinite number of channels?)
If anyone has any idea why errorMsg drops the initial lines or another approach that does not suffer from this problem, please let me know.
I know that this will come up, so I will say in advance that switching to Tcl 8.5 is probably not an option for me in the short term, since I do not control the environment in which this script is run.
I have a program read from stdin and process it. ( like "tee /some/file" )
This program wait stdin end to exit itself.
If I spawn it from Expect, after I send many content, how to send an "EOF" to the program?
there is a close command in Expect, but it will also send a SIGHUP, and can not expect program output anymore.
Expect works (on non-Windows) by using a virtual terminal which the spawned program runs within. This means that you can do things by sending character sequences to simulate keys. In particular, the EOF control sequence is done with Ctrl+D, which becomes the character U+000004. The terminal processes this to turn it into a true EOF.
There's a few ways to write it, depending on which escape sequence you prefer, but one of these will work:
# Hexadecimal-encoded escape
send \x04
# Octal-encoded escape
send \004
# UNICODE escape (also hexadecimal)
send \u0004
# Generate by a command
send [format "%c" 4]
When Expect is using Tcl 8.6, these all generate the same bytecode so use whichever you prefer.
I'm maintaining some old code and found that the following piece...
if {[catch {exec -- echo $html_email > $file} ret]} {
puts $ret
return 0
}
...breaks due to the first character of an HTML email being <, i.e.
couldn't read file "html>
<title>cama_Investigate 00000560554PONY1</title>
<style type="text/css">
...
...
...
which is interpreted as an I/O redirect operator. Previously this wasn't an issue because we were starting the emails with some headers, e.g.
append html_email "Content-Type : text/html; charset=us-ascii\n"
append html_email "Content-Disposition: inline\n"
I'm going to rewrite all this to use Tcl's native file I/O, so this question is mainly academic: What is the proper way to guard a variable's contents from being interpreted by the shell when passed to exec?
I'm using Tcl 8.0.5 and csh, but I'm interested in a general answer if possible.
Tcl's exec is funky, alas. It insists on interpreting an argument that starts with a < character as a redirect. (There are a few other ones too, but you're a bit less likely to hit them.) There isn't a good general workaround either except to write the data to a temporary file and redirect from that.
set ctr 0
while 1 {
set filename /tmp/[pid].[incr ctr].txt
# POSIX-style flags; write-only, must create or generate error
if {[catch {open $filename {WRONLY CREAT EXCL}} f] == 0} break
}
puts $f $html_email
close $f
exec echo <$filename >$file
file delete $filename
This is horribly complicated! We can do much better by changing what program we use. If instead of using echo we use cat, we can use exec's heredoc syntax:
exec cat <<$html_email >$file
Since in this case the characters are being passed directly via a pipeline (which is how Tcl does this) there's far less to go wrong. Yet it's still silly since Tcl's entirely capable of writing to files directly, more portably, and with less overhead:
set f [open $file "w"]
puts $f $html_email
close $f
Yes, this is actually a hugely simplified version of the general replacement from the first example above. Let's do the simple things that are much more obviously correct since then there's less to surprise in the future.
You can invoke the intended command indirectly, routing it through a shell:
exec -- csh -c "echo '$html_email'" > $file
or
exec -- csh -c "exec echo '$html_email'" > $file
I am running one tcl script who is taking file as a input by "stdin".The problem is that its taking the file content as a filename and throwing error while running the script on command line processor.
tcl script is
#!/bin/sh
# SystemInfo_2.tcl \
exec tclsh "$0" ${1+"$#"}
set traps [read stdin];
#set traps "snmp trap test"
set timetrap [clock format [clock seconds]];
set trapout [open Database_traps_event.txt a+];
set javaout [open JavaTrapOutput.txt a+];
puts $trapout $timetrap;
puts $trapout $traps;
puts $trapout "Before executing java program";
set javaprogargs "open {|java -cp mysql-connector-java-5.1.10.jar;. EventAlarmHandling \"$traps\"} r";
puts $trapout $javaprogargs;
set javaprogram [eval $javaprogargs];
puts $trapout "Execution of java is over"
while { [gets $javaprogram line] != -1 } {
puts $javaout $line;
}
close $javaprogram;
puts $trapout "After excution of java program\r\n\r\n\r\n\r\n\r\n";
close $trapout;
close $javaout;
exit;
input file content is -
<UNKNOWN>
UDP: [192.168.1.19]:60572->[0.0.0.0]:0
.iso.org.dod.internet.mgmt.mib-2.system.sysUpTime.sysUpTimeInstance 1:9:58:56.61
.iso.org.dod.internet.snmpV2.snmpModules.snmpMIB.snmpMIBObjects.snmpTrap.snmpTrapOID.0 .iso.org.dod.internet.snmpV2.snmpModules.snmpMIB.snmpMIBObjects.snmpTraps.linkDown
.iso.org.dod.internet.mgmt.mib-2.interfaces.ifTable.ifEntry.ifIndex.1 8
.iso.org.dod.internet.mgmt.mib-2.interfaces.ifTable.ifEntry.ifAdminStatus.8 up
.iso.org.dod.internet.mgmt.mib-2.interfaces.ifTable.ifEntry.ifOperStatus.8 down
From command line it ran like below
E:\eventAlarmHandling>tclsh TclTempFile.tcl < traps.txt
couldn't read file "UNKNOWN>
UDP: [192.168.1.19]:60572->[0.0.0.0]:0
.iso.org.dod.internet.mgmt.mib-2.system.sysUpTime.sysUpTimeInstance 1:9:58:56.61
.iso.org.dod.internet.snmpV2.snmpModules.snmpMIB.snmpMIBObjects.snmpTrap.snmpTrapOID.0 .iso.org.dod.intern
et.snmpV2.snmpModules.snmpMIB.snmpMIBObjects.snmpTraps.linkDown
.iso.org.dod.internet.mgmt.mib-2.interfaces.ifTable.ifEntry.ifIndex.1 8
.iso.org.dod.internet.mgmt.mib-2.interfaces.ifTable.ifEntry.ifAdminStatus.8 up
.iso.org.dod.internet.mgmt.mib-2.interfaces.ifTable.ifEntry.ifOperStatus.8 down": No error
while executing
"open {|java -cp mysql-connector-java-5.1.10.jar;. EventAlarmHandling "<UNKNOWN>
UDP: [192.168.1.19]:60572->[0.0.0.0]:0
.iso.org.dod.internet.mgmt.mib..."
("eval" body line 1)
invoked from within
"eval $javaprogargs"
invoked from within
"set javaprogram [eval $javaprogargs]"
(file "TclTempFile.tcl" line 26)
So clearly in command line its showing that "couldn't read file UNKNOWN> ......"
So please explain it that whats happening here in command line.I am new to tcl.So hoping that someone help me out.
Thanks
You're having problems with one of the trickier bits of how pipelines work in Tcl. If we look at the documentation carefully, we see:
If the first character of fileName is “|” then the remaining characters of fileName are treated as a list of arguments that describe a command pipeline to invoke, in the same style as the arguments for exec.
That means you have to have the first character be | and the rest, after stripping that first character, be a proper list. In your case, you've not got that. Instead, you're doing:
set javaprogargs "open {|java -cp mysql-connector-java-5.1.10.jar;. EventAlarmHandling \"$traps\"} r";
That's pretty complicated anyway. Let's build this in the idiomatic fashion instead:
set CPsep ";"
set classpath [list mysql-connector-java-5.1.10.jar .]
set javaprogargs [list open |[list \
java -cp [join $classpath $CPsep] EventAlarmHandling $traps]]
It helps to split the classpath out; it's got a ; character in it (on Windows; you'll need to change that if you port to Linux or OSX) and it's nicer to use list in Tcl to build things and then join to convert into what Java expects.
We also no longer need any backslash-quoted substrings in there (except the one I put in to keep lines short and readable); the pattern of list commands there will add everything that is required. Note the |[list …] there: that's non-idiomatic everywhere in Tcl except when creating a pipeline when it is recommended practice as it is doing in reverse what open expects to parse.
The other thing you're running into is this:
If an arg (or pair of args) has one of the forms described below then it is used by exec to control the flow of input and output among the subprocess(es). Such arguments will not be passed to the subprocess(es).
[…]
< fileName
The file named by fileName is opened and used as the standard input for the first command in the pipeline.
Your argument from $traps starts with a < and so it triggers this rule.
Unfortunately, there's no simple workaround for this and this is a severe, known, and very annoying limitation of the pipeline creation code. The only known techniques for dealing with this are to move to transferring that data by either a file or via the subprocess's standard input, both of which require modifying the subprocess's implementation. If you can make that Java program read from System.in (a good idea anyway, so you don't hit Windows's command line length limitations!) then you can pass the value like this:
set CPsep ";"
set classpath [list mysql-connector-java-5.1.10.jar .]
set javaprogargs [list open |[list \
java -cp [join $classpath $CPsep] EventAlarmHandling << $traps]]
That is just by adding a << in there immediately before the value.