I have inherited some code that is written in Perl and makes HTTP requests between the server and the client. I want to print few variables that is in the server code but that raises errors when I use the print statement. The variables are scalars, arrays or hashes. I want to print the output to the terminal and only for debugging purposes. Few errors I get are-
malformed header from script 'get_config': Bad header: self=$VAR1 = bless( {
Response header name 'self=Bio' contains invalid characters, aborting request
A simple print 'test' raises error like
malformed header from script 'get_config': Bad header: test
How do I print the variable values without any errors?
You haven't explained yourself very well at all. But, from the errors you're getting, I assume this is a CGI program.
A CGI program sends its output to STDOUT, where the web server catches it and processes it in various ways. In order for this to work, the data that your program prints to STDOUT needs to follow various rules. Probably the most important of those rules is that the first output from your program must be the CGI headers - and at the least, those headers should include a Content-type: header.
I assume that you're trying to display your debugging output before your program has sent the CGI headers. That's not going to work.
But do you really want to send your debugging output to STDOUT? That seems like a bad idea. If you use warn() instead of print() then your output will go to STDERR instead - and in most web servers, STDERR is connected to the web server's error log.
For more control over the output generated by warn(), see the CGI::Carp module.
Related
I am using Python's Paramiko library to SSH a remote machine and fetch some output from command-line. I see a lot of junk printing along with the actual output. How to get rid of this?
chan1.send("ls\n")
output = chan1.recv(1024).decode("utf-8")
print(output)
[u'Last login: Wed Oct 21 18:08:53 2015 from 172.16.200.77\r', u'\x1b[2J\x1b[1;1H[local]cli#BENU>enable', u'[local]cli#BENU#Configure',
I want to eliminate, [2J\x1b[1;1H and u from the output. They are junk.
It's not a junk. These are ANSI escape codes that are normally interpreted by a terminal client to pretty print the output.
If the server is correctly configured, you get these only, when you use an interactive terminal, in other words, if you requested a pseudo terminal for the session (what you should not, if you are automating the session).
The Paramiko automatically requests the pseudo terminal, if you used the SSHClient.invoke_shell, as that is supposed to be used for implementing an interactive terminal. See also How do I start a shell without terminal emulation in Python Paramiko?
If you automate an execution of remote commands, you better use the SSHClient.exec_command, which does not allocate the pseudo terminal by default (unless you override by the get_pty=True argument).
stdin, stdout, stderr = client.exec_command('ls')
See also What is the difference between exec_command and send with invoke_shell() on Paramiko?
Or as a workaround, see How can I remove the ANSI escape sequences from a string in python.
Though that's rather a hack and might not be sufficient. You might have other problems with the interactive terminal, not only the escape sequences.
You particularly are probably not interested in the "Last login" message and command-prompt (cli#BENU>) either. You do not get these with the exec_command.
If you need to use the "shell" channel due to some specific requirements or limitations of the server, note that it is technically possible to use the "shell" channel without the pseudo terminal. But Paramiko SSHClient.invoke_shell does not allow that. Instead, you can create the "shell" channel manually. See Can I call Channel.invoke_shell() without calling Channel.get_pty() beforehand, when NOT using Channel.exec_command().
And finally the u is not a part of the actual string value (note that it's outside the quotes). It's an indication that the string value is in the Unicode encoding. You want that!
This is actually not junk. The u before the string indicates that this is a unicode string. The \x1b[2J\x1b[1;1H is an escape sequence. I don't know exactly what it is supposed to do, but it appears to clear the screen when I print it out.
To see what I mean, try this code:
for string in output:
print string
How can I run a binary cgi file on the command line and provide GET parameters to it?
I understand this task may be straightforward for perl or php files, but I've got a binary cgi file and no documentation for it. I'd like to run it without a web server so that I can evaluate certain problems on some co-workers' machines.
I've tried the following, but to no avail:
QUERY_STRING="foo=bar" ./myfile.cgi
foo=bar ./myfile.cgi
./myfile.cgi foo=bar
./myfile.cgi <<< "foo=bar"
In each case, the script outputs Error in form found<br>Missing foo<br><b></b><br>. (When executed through apache on our server, it returns no error message, only the intended results.)
Specifying the environment variable REQUEST_METHOD=GET in addition to QUERY_STRING=... makes the difference.
Among the tokens output by strings myfile.cgi, there were a number of cgi-related variables which the web server might be expected to set, such as REMOTE_ADDR, SERVER_SOFTWARE, and SERVER_PROTOCOL, but the two aforementioned variables proved enough to get this executable to produce a non-error output.
(For a POST, I've read that the body/params are read from stdin, but I haven't substantiated that personally.)
I have a simple Jmeter test where I have a property to set the URL. The PATH in the Jmeter test is set to the following.
${__P(GET_URL,)}
This works well for all URLs that I have been working with, except for the ones where I need to pass a variable in the URL component.
For example, it works for http://server:port/getemployeelist when I run the test with -JGET_URL=/getemployeelist
Then I created a CSV config element to populate the variable EMP_ID.
Then if I run the test with -JGET_URL=/getemployee/${EMP_ID}, the EMP_ID variable is not getting substituted. Jmeter test gives me an error as follows:
java.net.URISyntaxException: Illegal character in path at index xx: https://://getemployee/${EMP_ID}
Appreciate any help/pointers.
It will not work this way, JMeter doesn't know anything about ${EMP_ID} at the time it is being started, you need to append this ${EMP_ID} to HTTP Request sampler "Path" in the runtime
Start JMeter as:
jmeter -JGET_URL=/getemployee/
Use CSV Data Set Config to read the EMP_ID from the CSV File
In the HTTP Request sampler use construction like /${__P(GET_URL,)}/${EMP_ID} to combine JMeter Property specified via -J command line argument and JMeter Variable originating from the CSV file.
If anything goes wrong first of all check jmeter.log file - it normally contains enough troubleshooting information. If there is nothing suspicious - use Debug Sampler and View Results Tree listener combination to inspect requests and response details, variables and properties names and values, etc.
Had asked this question a while back. Thought of posting the solution which I eventually ended up implementing. In the solution, I created a template jmx with a substitution variable for the HttpSampler.path and then replace the path at runtime. Following are the key points from the scripting done.
This turned out to be a simpler solution that worked for all kinds of API call patterns.
Created a template jmx (jmeter_test_template) with the following line.
<stringProp name="HTTPSampler.path">#PATH#</stringProp>
This jmx has CSV config element to populate variable "EMP_ID". To create this file, just create a new test with any URL and then save it as a template and replace the URL with substitution variable #PATH#.
Created a wrapper script like run_any_api.sh with usage,
sh run_any_api.sh URL=http://server:port/myapp/employees/${EMP_ID}
In the wrapper script, this URL is replaced in place of the token.
sed "s/#PATH#/$URL" jmeter_test_template.jmx > jmeter_test_template.current_test.jmx
jmeter -t jmeter_test_template.current_test.jmx
Last but not the least, please remember to cleanup the temporary jmx,
rm jmeter_test_template.current_test.jmx
I am trying to get my CGI scripts running on my web host (which runs on FreeBSD). To debug why I keep getting the dreaded "premature end of script headers" error, their support recommended that I redirect all my output to stderr, rather than printing it. Looking up how to do this, I came across a very old RAMBO ticket about it, but it looks like it was never implemented.
Per some of the answers to this question, it seems like I should be able to do a call {echo Hello, world >&2} to achieve this, but it doesn't work.
How can I write to stderr in REBOL2?
For my CGI-specific scenario, I have a truly awful workaround. Since writing to stderr in Perl (with which I am entirely unfamiliar) is a one-liner, I'm currently calling the REBOL script from Perl and printing its output to stderr from there:
#!/usr/bin/perl
use strict;
use warnings;
use CGI;
# Note the backticks
my $the_string = `/home/public/rebol -csw test-reb.cgi`;
print STDERR $the_string;
This webpage has some suggestions http://www.liquidweb.com/kb/apache-error-premature-end-of-script-headers/
to solve your real problem. Perhaps you did not have the headers printed as first thing in your script, this must be the first thing to do. Maybe the rights are not sufficient, or the .r file type was not properly added in your .htaccess as cgi able file. Your (correct!) rebol core exe has not the correct rights. Or your script ends up in an endless loop?
Some hints to redirect errors for Rebol cgi script:
http://www.rebol.com/docs/core23/rebolcore-2.html#section-6.2
Better late than never... I've just implemented it for Rebol3 in my Rebol fork.
https://github.com/Oldes/Rebol-issues/issues/2468
The syntax will be probably changed a little bit, because I don't like that the system console port is named input, although it is not just for the input.
So far it is:
print 1 ;<- std_out
modify system/ports/input 'error on
print 2 ;<- std_err
modify system/ports/input 'error off
print 3 ;<- std_out
I am trying a bit of experiments with airmon-ng script in Linux. Meanwhile i want to redirect output of a process "airodump-ng mon0" to a file. I can see the instantaneous output on the screen. The feature of this process is that it won't stop execution(actually it is a script to scan for AP and clients, it will keep on scanning) unless we use ctrl+c.
Whenever i try
airodump-ng mon0 > file.txt
i won't get the output in the file.
My primary assumption is that the shell will write it to the file only after completing the execution. But in the above case i stopped the execution(as the execution won't complete).
So to generalize i can't pipe the output of a running process to a file. How can i do that?
Or is there any alternative way to stop the execution of the process(for example after 5 seconds) and redirect the current output to a file?
A process may send output to standard output or standard error to get it to the terminal. Generally, the former is for information and the latter for errors, but in some cases, a process may mix them up.
I'm supposing that in your case, the standard error is being used. To get both of these to the output file, you can use:
airmon-ng mon0 > file.txt 2>&1
This says to send standard output to file.txt and to reroute 2 (which is the file id for standard error) into 1 (the file id for standard output) so that it also goes to the file.