Using process process.stdout.write to print to the console returns the string with true appended to the end
process.stdout.write is appending true to the value I want to print to the console.
I tried running the same command using node in the cli - same result
Command: node -p "process.stdout.write('hello')"
Console: hellotrue
I expected hello to appear.
I think you need to take another look at your code. some of the common advice for programming forums is to get an example simplified enough that your problem still occurs.
In this case if I write process.stdout.write('hello') to a file, and then ask node to run that file, I get the correct response of hello back, the word true doesn't show up.
According to the options from node, using -p instead of -e means you're asking it to print the result of that function call, which was a success.
-e, --eval script evaluate script
-p, --print evaluate script and print result
For now try the -e flag with your code.
Related
Is it possible to get a true/false value from a node script which also writes something into std output?
// node script
console.log('doing something');
if (doSomething()) {
return true; // I would like to get this in bash
}
return false; // Or this
Then in my bash I read it like this
SUCCESS=$(node script.js)
but the problem is that SUCCESS contains all the logging from console.log but not the return value.
In my environment, I can't use exit codes for this, otherwise the whole script fails.
There's a two main options for this I can see:
Return a status code, and use it carefully to ensure it doesn't crash your script, e.g:
SUCCESS=$((node script.js && echo 'ok') || echo 'fail')
This line always returns successfully, even if node returns a non-zero exit code. After this runs, SUCCESS will be set to either ok or fail, depending on the result - you can replace that with whatever logic you'd prefer.
Print output as the last line from your comand, and use node script.js | tail -n1 to collect only the last line of the output, and ignore the rest of the logging
I would recommend 1 if you can, but if you really need to avoid using status codes, or you need more complex output, you may want to go for option 2.
My Python 3.7.1 script generates a fasta file called
pRNA.sites.fasta
Within the same script, I call following system command:
cmd = "weblogo -A DNA < pRNA.sites.fasta > OUT.eps"
os.system(cmd)
print(cmd) #for debugging
I am getting the following error message and debugging message on the command line.
Error: Please provide a multiple sequence alignment
weblogo -A DNA < pRNA.sites.fasta > OUT.eps
"OUT.eps" file is generated but it's emtpy. On the other hand, if I run the following 'weblogo' command from the command line, It works just find. I get proper OUT.eps file.
$ weblogo -A DNA<pRNA.sites.fasta>OUT.eps
I am guessing my syntax for os.system call is wrong. Can you tell me what is wrong with it? Thanks.
Never mind. It turned out to be that I was not closing my file, "pRNA.sites.fasta" before I make system call that uses this file.
When type a unterminated command in a mongo shell, it will return three dots indicating need more input to complete this command like below:
> db.test.find(
... {
...
I am using nodejs child_process.spawn to create a mongo shell process and listen on its output. I can get the standard and error output from the mongo shell but I can't get the ... output. Below is my nodejs code:
const shell = spawn('mongo', params);
shell
.stdout
.on('data', (data) => {
winston.debug('get output ' + data);
});
shell
.stderr
.on('data', (data) => {
const output = data + '';
winston.error('get error output ', data);
});
I run below code to send command on the shell:
shell.stdin.write('db.test.find(');
I wander why I can't get the ... output on above method. Is it a special output?
EDIT1
I tried to use node-pty and pty.js. They can get the ... output but they mix the input and output data together. It is not possible to separate them.
I also tried to use stdbuf and unbuffer to disable buffer but it still doesn't work.
It seems that nodejs child_process doesn't work well with interactive command.
Your code doesn't include anything that writes to the stdin of your child process so I would be surprised if you got the ellipsis that indicates incomplete command when in fact you don't send any command at all - incomplete or otherwise.
That having been said, many command line utilities behave differently when they discover a real terminal connected to their stdin/stdout. E.g. git log will page the results when you run it directly but not when you pipe the results to some other command like git log | cat so this may also be the case here.
This can also have to do with the buffering - if your stream is line-buffered then you won't see any line that is not ended with a newline right away.
The real question is: do you see the > prompt? Do you send any command to the mongo shell?
Scritping interactive CLI tools can be tricky. E.g. see what I had to do to test a very simple interactive program here:
https://github.com/rsp/rsp-pjc-c01/blob/master/test-z05.sh#L8-L16
I had to create two named pipes, make sure that stdin, stderr and stdout are not buffered, and then use some other tricks to make it work. It is a shell script but it's just to show you an example.
I execute a program which print some texts. I redirect the texts to file by using > but I cannot see any texts on the file. For example, if the program prints "Hello" I can see the result on the shell:
$ ./a.out arg
Hello
But after I redirect I cannot get any message hello on shell as well as the redirected file.
$ ./a.out arg > log.txt
(print nothing)
$ cat log.txt
(print nothing)
I have no idea what's going on. Is there someone who knows what's happening here? Or is there someone who suffered similar situation?
OS: Ubuntu 14.10, x86_64 arch, and the program is really chromium-browser rather than ./a.out. I edited its JavaScript engine (v8, which is included in chromium-browser) and I tried to print some logs with lots of texts. I tried to save it by redirection but it doesn't work.
Surely I checked whether > symbol work or not. It works as expected on other programs like echo, ls, and so on.
$ echo hello > hello.txt
$ cat hello.txt
hello
How can the messages just go away? I think it should be printed on stdout (or stderr) or file. But it just goes away when I use > symbol.
It is somewhat common for programs to check isatty(stdout) and display different output based on whether stdout is connected to a terminal or not. For example, ls will display file names in a tabular format if output is to a terminal, but display them strictly one per line otherwise. It does this to make it easy to parse its output when it's part of a pipeline.
Not having looked at Chrome's source code myself, this is speculation, but it's possible Chrome is performing this sort of check and changing its output based on where stdout is redirected to.
Try to use "2>" which should redirect stderr to file
Or you can also try to use "&>" which should redirect everything (stderr and stdout)
See more at http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-3.html
I'm writing a script to test a program and I'm getting caught at this portion
if (("$x"==22)); then
echo "Checking for whether wrong input file is detected."
if diff ${arr[$x]} <(./compare ); then
echo Output is as expected.
else
echo Output is not as expected. Check for errors.
fi
else
if diff -q ${arr[$x]} <(./compare $i); then
echo Output is as expected.
else
echo Output is not as expected. Check for errors.
fi
fi
So what it's doing is testing my program against known output. However, for the case where I use ./compare without an argument, I want to receive an error message from my program specifying that the argument is missing. The test file it's using, "22" let's call it result22.txt, has the exact same output my program would give from just running ./compare (no arguments). However, when I run it using the script, it says that result22.txt differs from just running ./compare. I'm pretty sure I"m running the script wrong, any ideas?
Additionaly information, i is a known input test file that's from an array, x is an incremental variable to count which loop we're on. So arr[$x] is just accessing the nth file from the known output files.
Compare is my own compare program to run.