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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1answer
46 views

patch: “bad file descriptor” in combination with pipe and LD_PRELOAD/ libtrash

Very short summary: cat "$file" | patch produces a Bad file descriptor-error, but patch < "$file" works, when libtrash is preloaded with LD_PRELOAD, and only on bigger projects. Description: For ...
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2answers
100 views

Why does the cd command handle STDIN different than other commands?

Commands like cd cannot have output piped to them in order to change directories--they require command-line arguments. Why does the cd command (and those similar to it, such as mv, cp, & rm) not ...
3
votes
3answers
39 views

How to pipe data from one command to another command which allows only a file as an argument?

I have some arbitrary data as an output of a command (e.g. a fragment of a binary data put out using tail). I want to feed it to another command/program which allows only a file as an argument (e.g. ...
2
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1answer
46 views

How do I turn entire stdin into a command line argument verbatim?

Attempt 1 xargs -I '{}' -0 -n 1 myprogram --arg '{}' --other-options But that does not preserve zero bytes. Also the program may run multiple times. But instead of failing in case of zero byte ...
6
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5answers
4k views

Bash script that reads filenames from a pipe or from command line args?

I want my script to read a bunch of filenames (which may have spaces) given either as a glob or from STDIN and do stuff with them. I've been able to read either way separately, but not combine them. ...
19
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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
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1answer
38 views

Why doesn't cc (the C compiler) and similar utilities use standard streams by default? [closed]

Background If think most of us agree that filters and pipes are the very foundation of Unix systems. Pipes and filters are very powerful tools. Almost all Unix utilities use the standard input and ...
2
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1answer
45 views

How to trick an application expecting a file:// to read from stdin?

A file URI scheme makes it possible to specify an URI to a file stored locally, such as file:///home/demo/sample. Could it be used to specify stdin? For instance, with CURL: curl ...
0
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1answer
33 views

vimdiff to compare output instead of files

I am trying to compare two command output (no files) vimdiff "$(tail /tmp/cachain.pem)" "$(tail /etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem)" I tried playing with redirection, pipe, and vim - ...
0
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2answers
84 views

While loop for bash scripting to read either stdin or arguments

I'm playing around with the accepted answer from this thread: Bash script that reads filenames from a pipe or from command line args? When I use the below script, efetch ...
1
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1answer
325 views

Identify when 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 want to have to press enter each time to the script. Instead, I ...
1
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1answer
33 views

Trying to redirect <enter> and second response to linux shell script

I'm trying to automate a process that creates a binary response file using a java program wrapped by a sh script (so many things wrong with this, but not my code). The result I want requires hitting ...
4
votes
3answers
809 views

Bash, name of the stdin file?

I have to write a bash script which will count symbols like "<" and ">" from stdin. For example: $ ./myscript.sh <example.html > - 20 < - 21 Found mismatching brackets! I did this: ...
1
vote
2answers
90 views

Duplicate stdin to stdout and stderr, but in a synchronized way

I need to duplicate the stdout of a producer and feed it to two consumer in a synchronized fashion. consumer 1 producer | duplicator | consumer 2 ...
6
votes
3answers
261 views

Are unix[-like] programs capable of determing where their output is going? [duplicate]

Up until recently I was under the impression that Unix-y programs were unaware of where their output went, be it to standard out, redirected to a file, or into a pipe. However, an unrelated U&L ...
6
votes
2answers
99 views

Notification Listener Behaving Strangely when Backgrounded

I've been struggling to get my IRC-Bouncer/Notification Script working. This is meant to be a script which will automatically login to a remote machine, attach to a screen session (or start one if ...
0
votes
2answers
64 views

Interactively remove files in loop with standard input redirection

I need to interactively (i.e. rm -i) remove files stored in variable $to_remove (one path per line). Unfortunately my code doesn't work because standard input is already used by redirection ...
37
votes
8answers
10k views

How to do nothing forever in an elegant way?

I have a program which produces useful information on stdout but also reads from stdin. I want to redirect its standard output to a file without providing anything on standard input. So far, so good: ...
7
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2answers
20k 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 ...
4
votes
2answers
249 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 ...
6
votes
3answers
132 views

Peek at the contents of stdin

I'm trying to debug a Linux application that can receive commands via stdin, and it would be really useful to be able to see everything that gets written to stdin. My first approach was to execute ...
3
votes
3answers
85 views

Wait for key in shell script that may get piped to /bin/bash

Consider the following shell script echo foo; read; echo bar Running bash my_script outputs 'foo', waits for the return key and outputs 'bar'. While this works fine running it that way, it doesn't ...
1
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3answers
98 views

How to write a script that can take input from stdout

I want to be able to write a script that can take stdout as an argument, if anything is piped into it (ultimately, I would like it to be polymorphic) - The trouble is, I have searched and searched ...
3
votes
2answers
264 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 ...
17
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, ...
3
votes
4answers
189 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 ...
1
vote
1answer
134 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
637 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 ...
6
votes
1answer
358 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 ...
1
vote
2answers
376 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: ...
13
votes
3answers
3k 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 ...
3
votes
2answers
139 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
240 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
34 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?
6
votes
3answers
2k views

Create a virtual file that is actually a command

Is there any way to create a virtual file, such that reading from the file actually reads from the stdout of a command; writing to the file is acually writing to the stdin of a command? So far I have ...
1
vote
1answer
49 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 ...
5
votes
3answers
259 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 ...
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votes
0answers
41 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 ...
1
vote
2answers
1k views

run a remote process via autossh in background

In Ubuntu I'm trying to run the geany editor on my local X display via the command: autossh -o StrictHostKeyChecking=false -XCg me@otherDYNDNShost geany & Trouble is, after the first ...
3
votes
1answer
55 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" ...
7
votes
3answers
2k views

Construct a command by putting a string into a tty

I managed to do this echo -n "command" > /dev/tty1 The letters appear, and the cursor moves, but they are "ghosts" - if you hit enter, nothing happens (they are not in stdin). Edit: In the ...
42
votes
5answers
18k views

Can I pipe stdout on one server to stdin on another server?

stdout on one CentOS server needs to be piped to stdin on another CentOS server. Is this possible? Update ScottPack, MikeyB and jofel all have valid answers. I awarded the answer to Scott because, ...
1
vote
2answers
78 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 ...
5
votes
3answers
597 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 ...
1
vote
2answers
255 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. ...
0
votes
1answer
931 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
397 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
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2answers
2k 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
1answer
193 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?
1
vote
2answers
895 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 ...