stdin is the name of the default input file descriptor of a process. Since there is really nothing special about `stdin`, you *should not* use this tag. Use [tag:io-redirection] for questions on how to redirect input, use [tag:file-descriptors] for questions on how to manage file descriptors, use ...

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3
votes
2answers
51 views

How do I filter stdout of a program through grep while still controlling the program?

I'm trying to filter the output of the mpv media player, removing a particular line, but when I do so I am unable to control mpv with the keyboard. Here is the command: mpv FILE | grep -v 'Error ...
3
votes
4answers
129 views

Provide strings stored in a file as a list of arguments to a command?

I install a list of URLs in a text file named myurls: http://www.examples.com/1 http://www.examples.com/2 http://www.examples.com/3 How shall I pass these URLs to wkhtmltopdf as inputs? The direct ...
15
votes
3answers
2k views

How to “less” a file named “-”?

I accidentally created a file with the name - (eg, seq 10 > -). Then I tried to use less to view it, but it just hangs. I understand that this is happening because less - expects input from stdin, ...
1
vote
1answer
39 views

TTY control characters sent to stdin of sh doesn't work

I tried to develop a remote app that launches sh and resends an incoming data there, and found that some special sequences don't work. So, for testing purposes, I launched on my desktop sh, then ...
4
votes
4answers
371 views

How can I get the size of stdin?

I'm about to compress a large directory and I want to know how large, exactly, the resulting file will be. I've tried using du: $ tar -cv dir | du -h - du: cannot access '-': No such file or ...
1
vote
2answers
33 views

How to pass password to mysql command line

I have MySQL password saved on a file foo.php, for example P455w0rd, when I try to use it: $ cat foo.php | grep '$dbpwd=' | cut -d '"' -f 2 | mysql -U root -p mydb -h friendserver Enter password: ...
6
votes
1answer
90 views

Terminal does not accept pasted or typed lines of more than 1024 characters [duplicate]

When I enter text on stdin in an OS X Terminal, a single line is limited to 1024 characters. For example, cat > /dev/null beeps after I type (or paste) a line longer than this, and refuses to ...
3
votes
2answers
55 views

Remove data from the STDIN stream buffer of another TTY session

I encountered a problem the other day while running multiple tty sessions in separate terminal windows. I was running a expensive disk access command and was waiting for it to return. Meanwhile I was ...
0
votes
1answer
70 views

OpenVPN via systemd fails with stdin error

OpenVPN starts and runs just fine when I invoke it directly from the command line, but when I try to start it as a process via systemd, it throws a failure error that I can't find a solution to. ...
-1
votes
1answer
27 views

Does those two constructions do the same thing: proces <input.txt vs cat input.txt | process in Linux

Does those two constructions do the same thing: proces <input.txt vs cat input.txt | process in Linux?
4
votes
1answer
110 views

uniq and bash for loop not writing to stdout before stdin closing (for one-line website visitor notification system)

I'm trying to trigger a beep on the PC speaker for every unique visitor of a website. After some brainstorming, it seemed to be possible with one line: for e in `ssh me@mymachine "tail -n 1 -f ...
1
vote
1answer
41 views

Bourne shell: ignoring certain kinds of stdin

I have a program that is currently working, but I need to modify it to ignore some stdin that is not fitting for its correct function. Right now, to run the program: printf "1\n3\n5\n" | sh prog The ...
0
votes
0answers
30 views

stdin read notification

I want to detect when/if an application issues read(stdin, ...). Is it possible to use unbuffered I/O so that I could wait on write in external process? The problem: Some commands require user input ...
3
votes
1answer
45 views

Question about interactive detection in bash

I have a question about interactive detection in bash. The following script prints if it is called in interactive mode or not. $ cat int.sh #!/bin/bash if [ -t 0 ]; then echo "interactive" ...
1
vote
2answers
50 views

Using find and aspell together

I'm trying to spell check all the *.md files in my current directory but the following command fails: >> find . -maxdepth 1 -name "*.md" | xargs -I {} aspell check {} xargs: aspell: exited with ...
19
votes
3answers
1k views

Is it safe to type another command into STDIN while the previous command is writing to STDOUT?

Perhaps this has been answered previously, I would welcome a link to another answer... If I execute a shell command (in a bash shell) like the following: make Then while the output from make is ...
1
vote
2answers
113 views

Stdin Input Behavior Between “cat” and “less”

When I issue cat, the terminal hangs waiting for stdin input. However, when less is issued, I get Missing filename ("less --help" for help). It is known that both less and cat accepts stdin input. ...
5
votes
3answers
230 views

Echoing stdin when running an ed(1) script

Given the following ed script, $ cat helloworld a hello world . ,n ,s,o,O,g ,n Q I would like to obtain somehow the interactive output $ ed a hello world . ,n 1 hello 2 world ,s,o,O,g ,n 1 ...
0
votes
1answer
379 views

Command that prints file contents given filename on stdin

I have a command that produces some output part of which is actually a file name containing the full output data. I want to extract the file name (which I trivially do with cut) and then pass it to ...
3
votes
1answer
162 views

Run vsim from dmenu — it only works when directly invoked in the terminal

Works: vsim, sh -c vsim Doesn't work: echo "vsim" | sh, echo "vsim" | xargs -I {} sh -c "{}" I want to run ModelSim (vsim) with dmenu, which is triggered using xbindkeys. Details vsim is a ...
1
vote
2answers
983 views

Redirect stdin and stdout to ports

I'd like to take a program P that reads from stdin & writes to stdout, but connect it to nc or whatever such that it reads from a certain port and outputs to another port. # The reading is easy, ...
0
votes
2answers
414 views

cat STDIN won't work twice in script

I have a script that outputs various information and the text fields of an html form (method POST). When I attempt to cat <&0, it displays properly. However a few lines down, I try to cat ...
0
votes
1answer
122 views

Can pocketsphinx_continuous read from stdin?

There is one parameter -adcdev "Name of audio device to use for input.", but it doesn't say if this can be stdin. Can pocketsphinx_continuous read from stdin?
0
votes
0answers
124 views

Text replace literally *all* instances of a string through stdin, stdout

Linux, or specifically Ubuntu 14.04 LTS Server if necessary (and CENTOS 6.5/7 minimal would be nice). If I enter "FOO" at the command line, (regardless of whether as a word or as a substring), I'd ...
0
votes
6answers
119 views

What are some practical uses of STDIN redirection? [closed]

I am having a very difficult time trying to think of a single practical use for STDIN redirection. cat < /etc/passwd is an example of STDIN redirection, but it is silly in the same way as a useless ...
1
vote
1answer
87 views

What is happening while executing this command cd / | vi?

When I execute the command cd / | vi, it goes to the vi editor. When I type any command it does not display the command but it gets executed and the command that is executed is not shown in the ...
9
votes
2answers
402 views

Bash: process substitution and stdin

The following line is obvious: echo "bla" | foo | bar But does the ones below do the same? echo "bla" | bar <(foo) echo "bla" | bar < <(foo) Which of the foo and bar read "bla" from ...
1
vote
1answer
76 views

Is bluetooth keyboard associated with `stdin`?

I know that keyboard is standard input and is referred by the stdin file. I sometimes use a Bluetooth(BT) keyboard when working on my laptop. Both keyboards, my laptop keyboard as well as the BT ...
3
votes
1answer
95 views

Does cat never read from terminal?

Chapter 43. Redirecting Input and Output of Unix Power Tools, Third Edition has to say this about cat command: Standard input (stdin) normally comes from your keyboard. Many programs ignore ...
3
votes
1answer
210 views

How does `stdin` of linux work?

I know that stdin refers to standard input in linux, usually the keyboard. It can also be referred by file descriptor 0. So, which file descriptor does the (standard input) mouse refer to? Or is it a ...
3
votes
2answers
97 views

Decoding “prog > file 2>&1”

I am having some difficulty understanding the construct prog > file 2>&1. I have read that it means "Send stdout and stderr to file". But my question is how? I understand that prog > ...
11
votes
3answers
2k views

Why do some commands not read from their standard input?

I wonder what when we should use pipeline and when we shouldn't. Say for instance, to kill certain process which handling pdf files, the following will not work by using pipeline: ps aux | grep pdf ...
1
vote
1answer
107 views

Bash script and stdin

I am having a C program which requires to read from stdin. This is one of the requirements, and it cannot change. I have written a simple bash script that creates all the directories I want, handles ...
1
vote
1answer
209 views

Identify python script is waiting for a manual input

I'm writing a shell script which executes a Python script. The Python script halts for a manual enter to be provided. However, I don't wan't to have to press enter each time to the script. Instead, I ...
4
votes
2answers
781 views

using _< instead of < for stdin using bash

What is the difference between using _< and < for stdin when using process substitution. This is done using bash. Example: read bytes _< <(du -bcm random_iso.iso | tail -1); echo ...
5
votes
3answers
4k views

stdin, stderr, redirection and logs

Is there a difference between those two lines ? /home/user/script.sh >> /home/user/stdout_and_error.log 2>&1 /home/user/script.sh 2>&1 >> /home/user/stdout_and_error.log ...
12
votes
3answers
1k views

tee stdout to stderr?

I'd like to send stdout from one process to the stdin of another process, but also to the console. Sending stdout to stdout+stderr, for instance. For example, I've got git edit aliased to the ...
5
votes
3answers
412 views

Piping commands, modify stdin write to stdout

echo Hello World | nano - | less I want to modify Hello -> Goodbye while in the the text editor. It does not have to be with nano. I am stuck with nano reading stdin but requiring me to write to a ...
4
votes
1answer
7k views

Linux : how to redirect stdout & stderr to logger?

I have a program I need to run at startup, it has output on stdout and stderr that I want to redirect to the system log using the logger command. What I have in my startup script is thie: ...
2
votes
3answers
244 views

How do I make pasted shell commands invisible?

I'm using an AutoHotkey macro to run some shell commands, i.e. ^`:: SendInput set c=".cshrc-acheong"{ENTER} SendInput set v=".vimrc-acheong"{ENTER} SendInput foreach d ( /home/acheong /home/tcama ...
4
votes
2answers
398 views

Is there a way to 'tee' input to a program or script?

I'm trying to find a way to use an input file for a program in such a way that I can also use stdin. For example, say I have a SQL script that creates a table. I invoke it like this: mysql -p ...
0
votes
2answers
66 views

file(1) command termination when using the -f - option

Say I'd like to use the file -f - command inside a script, and send some input using the stdin, when I'm finished I'd like to terminate it gracefully, but unfortunately I haven't found any way to do ...
6
votes
1answer
690 views

bash scripting - read tarball from stdin

I have a task I need to script that I feel should be stupidly simple, but I'm actually having a rather tough time. I have a short bash script that takes a specific type of application in tarball form ...
-4
votes
2answers
113 views

What is the utility of piping to `/dev/null`?

Seeing that /dev/null's utility isn't immediately obvious to me, what is the use of /dev/null piping?
1
vote
1answer
273 views

Bash Script which can direct stdin stream to program

I am trying to create a script capable of infinitely processing an incoming stream which is piped to it, and continuous producing an output stream which can be piped to something else something as ...
3
votes
1answer
85 views

What is the relationship between a program's output, standard output, and its file descriptors?

Let's assume that I am running wget which is downloading something. It's printing some text to my terminal and writes the downloaded data into a file. From a terminology point of view, what is the ...
4
votes
3answers
396 views

processing command output line by line, without mixing standard input

So, I have a problem very similar to Bash: How to read one line at a time from output of a command?, I am doing: while read path; do mplayer $path; done < <(find-me-random-mp3s) or ...
5
votes
1answer
13k views

nohup: ignoring input and redirecting stderr to stdout

I am starting my application in the background using nohup as mentioned below - root@phx5qa01c:/bezook# nohup java -jar ./exhibitor-1.5.1/lib/exhibitor-1.5.1-jar-with-dependencies.jar -c file ...
7
votes
2answers
1k views

Piping data to a process's stdin without causing EOF afterward

I have an executable that starts a user-interactive shell. I would like to, upon launch of the shell, inject a few commands first, then allow the user to have their interactive session. I can do this ...
3
votes
1answer
136 views

How can I make stdin always get consumed?

Some programs do not read from stdin (such as dmesg or adb logcat). I usually press Return a few times to provide a separation between log lines. When I interrupt the command directly in the shell, ...