Standard input (stdin, file descriptor 0) is the input stream to a program.
Questions tagged [stdin]
3861 questions
1748
votes
25 answers
How do I read from stdin?
How do I read from stdin? Some code golf challenges require using stdin for input.
tehryan
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341
votes
12 answers
How do I pass a string into subprocess.Popen (using the stdin argument)?
If I do the following:
import subprocess
from cStringIO import StringIO
subprocess.Popen(['grep','f'],stdout=subprocess.PIPE,stdin=StringIO('one\ntwo\nthree\nfour\nfive\nsix\n')).communicate()[0]
I get:
Traceback (most recent call last):
File…
Daryl Spitzer
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324
votes
10 answers
Best practices with STDIN in Ruby?
I want to deal with the command line input in Ruby:
> cat input.txt | myprog.rb
> myprog.rb < input.txt
> myprog.rb arg1 arg2 arg3 ...
What is the best way to do it? In particular I want to deal with blank STDIN, and I hope for an elegant…
griflet
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323
votes
22 answers
How to read from a file or standard input in Bash
The following Perl script (my.pl) can read from either the file in the command line arguments or from standard input (STDIN):
while (<>) {
print($_);
}
perl my.pl will read from standard input, while perl my.pl a.txt will read from a.txt. This…
Dagang
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304
votes
11 answers
Confused about stdin, stdout and stderr?
I am rather confused with the purpose of these three files. If my understanding is correct, stdin is the file in which a program writes into its requests to run a task in the process, stdout is the file into which the kernel writes its output and…
Shouvik
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262
votes
10 answers
How to read from stdin line by line in Node
I'm looking to process a text file with node using a command line call like:
node app.js < input.txt
Each line of the file needs to be processed individually, but once processed the input line can be forgotten.
Using the on-data listener of the…
Matt R. Wilson
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221
votes
6 answers
Send string to stdin
Is there a way to effectively do this in bash:
/my/bash/script < echo 'This string will be sent to stdin.'
I'm aware that I could pipe the output from the echo such as this:
echo 'This string will be piped to stdin.' | /my/bash/script
Uyghur Lives Matter
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206
votes
8 answers
How to open every file in a folder
I have a python script parse.py, which in the script open a file, say file1, and then do something maybe print out the total number of characters.
filename = 'file1'
f = open(filename, 'r')
content = f.read()
print filename, len(content)
Right…
B.Mr.W.
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194
votes
10 answers
How to trick an application into thinking its stdout is a terminal, not a pipe
I'm trying to do the opposite of "Detect if stdin is a terminal or pipe?".
I'm running an application that's changing its output format because it detects a pipe on STDOUT, and I want it to think that it's an interactive terminal so that I get the…
Chris
159
votes
9 answers
How to pass the value of a variable to the standard input of a command?
I'm writing a shell script that should be somewhat secure, i.e., does not pass secure data through parameters of commands and preferably does not use temporary files. How can I pass a variable to the standard input of a command?
Or, if it's not…
user283145
148
votes
8 answers
nodejs how to read keystrokes from stdin
Is it possible to listen for incoming keystrokes in a running nodejs script?
If I use process.openStdin() and listen to its 'data' event then the input is buffered until the next newline, like so:
// stdin_test.js
var stdin =…
bantic
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148
votes
3 answers
Compress files while reading data from STDIN
Is it possible to compress (create a compressed archive) data while reading from stdin on Linux?
Space
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142
votes
6 answers
Detect if stdin is a terminal or pipe?
When I execute "python" from the terminal with no arguments it brings up the Python interactive shell.
When I execute "cat | python" from the terminal it doesn't launch the interactive mode. Somehow, without getting any input, it has detected that…
Mike McQuaid
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votes
14 answers
How to read a line from the console in C?
What is the simplest way to read a full line in a C console program
The text entered might have a variable length and we can't make any assumption about its content.
pbreault
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5 answers
How to pipe input to a Bash while loop and preserve variables after loop ends
Bash allows to use: cat <(echo "$FILECONTENT")
Bash also allow to use: while read i; do echo $i; done
Wakan Tanka
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