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

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28
votes
4answers
8k 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, ...
23
votes
4answers
4k 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: ...
21
votes
3answers
764 views

How can I limit the output speed of stdout?

I'm running CentOS 5.7 and I have a backup utility that has the option of dumping its backup file to stdout. The backup file is rather large (multiple gigabytes). The target is an SSHFS filesystem. To ...
13
votes
2answers
804 views

How to find out what process is writing to STDOUT?

I have two instances of a process running. One of them is "frEAkIng oUT!" and printing errors non stop to STDOUT. I want to kill the broken process but I have to make sure I don't terminate the wrong ...
13
votes
2answers
742 views

Redirect stderr from an already running script

I've been running a script for several days now. I redirected stdout to $HOME/mylog, but didn't redirect stderr since I thought there would be nothing on it. Suddenly thousands of lines started coming ...
10
votes
2answers
1k views

Script to quickly test all keyboard keys

I need to check some notebooks for bad keyboard keys, and so I'd like to speed that up as much as possible. I found nothing for this specific task, so my idea is a script that reads the pressed keys ...
9
votes
3answers
760 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 ...
9
votes
2answers
258 views

How a piped shell programs balance their output/input rates? [duplicate]

Possible Duplicate: Bash while loop and reading from pipe I come from web programming background, and find myself interested in one peculiarity of using a local shell. I understand that ...
9
votes
3answers
497 views

Is there a way to execute a native binary from a pipe?

echo 'main(){}' | gcc -xc - -o /dev/stdout | ??? Is there a way to run the output binary on a unix-like system? EDIT: I needed it to run the output of g++ in a sandboxed environment where I can't ...
8
votes
1answer
291 views

Output of command not in stderr nor stdout

I've stumbled on this issue, so I'm wondering how is this possible? Standard run of command: # zabbix_sender -c zabbix_agentd.conf -k mmysql.QCInserts -o 14 info from server: "Processed 0 Failed 1 ...
8
votes
3answers
6k views

bash: Use a variable to store stderr|stdout redirection

Is there any way to redirect stdout and stderr via variable like adding command options in script? For example I have a script: #!/bin/bash -x TEST=">/dev/null 2>&1" OPT='-p -v' mkdir $OPT ...
7
votes
5answers
2k views

Output file contents while they change

I want to output a file's contents while they change, for example if I have the file foobar and I do: magic_command foobar The current terminal should display the file's contents and wait until, I ...
7
votes
3answers
2k views

How do I make python programs behave like proper unix tools?

I have a few Python scripts laying around, and I'm working on rewriting them. I have the same problem with all of them. It's not obvious to me how to write the programs so that they behave like ...
7
votes
2answers
5k views

Execute command in remote active terminal

Suppose you have a terminal emulator (T1) open with a PID of 6350. From another terminal, type this command (C1): echo "ls\n" > /proc/6350/fd/0 This writes ls and the new line in T1 but does ...
7
votes
2answers
293 views

Kill a process if it goes quiet for a certain amount of time

I have a utility that has a nasty habit of going quiet and staying there, I already know how long into the process it does this so I am using timeout to fight this, but sometimes it does it before ...
6
votes
2answers
3k views

what is meant by connecting STDOUT and STDIN?

This is a newbie question. I'm reading a book, it says: Every process has at least three communication channels available to it: “standard input” (STDIN), “standard output” (STDOUT), and ...
6
votes
2answers
2k views

GNU screen: print a detached session to stdout

I just want to have a quick overview of my detached GNU screen sessions. Is it possible to dump the current content to stdout ? Something like screen --print SESSION_NAME > file.txt
5
votes
3answers
5k views

bash: /dev/stderr: Permission denied

After upgrading to a new release version, my bash scripts start spitting errors: bash: /dev/stderr: Permission denied in previous versions Bash would internally recognize those file names (which is ...
5
votes
4answers
270 views

How to send stderr to stdout with a pipe to another command?

I'm trying to capture all of the output of a build operation, and send it to myprogram. I seem to only be able to capture part of it. This is what I'm trying: make clean && make ...
5
votes
3answers
2k views

Output to stdout and at the same time grep into a file

I have a script that outputs text to stdout. I want to see all this output in my terminal, and at the same time I want to filter some lines and save them in a file. Example: $ myscript Line A Line B ...
5
votes
2answers
244 views

Write lines to a file from less

While in vim I can write a range of lines from the file I'm viewing to another file. For example, :1,10 w outfile.txt will write lines 1 through 10 to outfile.txt. Can I do the same while I'm ...
5
votes
2answers
610 views

Wrapping a shell script with tee

There is a bash script which prints some logs and allows some arguments. The script prints the logs to STDOUT. Let's say the script's name is AAA.sh I'd also like to make the script to print the logs ...
5
votes
2answers
1k views

Why does `cat`ing a file into itself erase it? [duplicate]

Possible Duplicate: IO redirection and the head command I just wanted to remove all but the first line of a file. I did this: head -1 foo.txt ... and verified that I saw only the first ...
5
votes
1answer
74 views

Is it possible to create sticky redirection from stdout/stderr

Consider such code: echo hello >> log.txt echo world >> log.txt I execute command with stdout redirection. Is it possible to create sticky redirection? Something like this: redir ...
5
votes
1answer
902 views

Append output to a file and redirect stderr to null

How can I append the result of a command to a file and redirect stderr to null?
5
votes
1answer
383 views

`unbuffer` or `stdbuf` for removing stdout buffering?

Is there a difference between unbuffer(1) and stdbuf(1)? From what I gather, unbuffer makes more than the "best effort" of calling the libc function set(X)buf at the beginning, and then letting things ...
5
votes
1answer
104 views

Rotating log files while process still running

I have a process running that writes standard output and standard error to a log file /var/log/dragonturtle.log. Is there anyway to rotate the log file, and have the process continuing to write to the ...
5
votes
2answers
802 views

Why jobs aren't killed at logout when executed with “> /dev/null 2>&1 &”?

When you run jobs like the example below, they're killed when you logout: $ ./job.sh & However, when you execute them as in the below example, redirecting stdout to /dev/null and stderr to ...
5
votes
1answer
552 views

Is it possible to “fork” STDOUT to two different locations? [duplicate]

Possible Duplicate: Is there a way in bash to redirect output and still have it go to stdout? Let's say I do: ps -ef | grep httpd to see if apache is running or not, but I also want to ...
5
votes
2answers
89 views

How can I pipe stdout to another program?

I'm trying to setup a linter for my code and I only want to lint the coffeescript files that have changed in the current branch. So, I generate the list of files using git: git diff --name-only ...
5
votes
1answer
37 views

IO and other shell commands when a program is not started by a terminal

I have several launchers on my desktop for various programs, and there is a "run in a terminal" setting for those launchers. When I check that setting, the program runs from a terminal, and logs its ...
4
votes
6answers
493 views

Command to output file content to stdout?

I know cat can do this, but its main purpose is to concatenate rather than just displaying the content. I also know about less and more, but I'm looking for something simple (not a pager) that just ...
4
votes
4answers
367 views

Reuse last line of output from shell command

I am compiling something and depending on success (last line of output contains "success"= I want to scp the binary to the target. I'd prefer a piped oneliner. Is there a way to do this?
4
votes
4answers
284 views

A command that generates both standard error and output

I want to do some troubleshooting on my bash script. Is there a short and simple command that generates both stdout and stderr so that I can use 2>&1 on it? Sorry if this looks trivial, but I ...
4
votes
2answers
849 views

Can I read and write to the same file in Linux without overwriting it? [duplicate]

Possible Duplicate: How can I make iconv replace the input file with the converted output? I frequently connect to amazon ec2 using their public DNS names ...
4
votes
4answers
197 views

Any way to cat few lines of man page to show on stdout for reference?

This is a simple question. Trying my best to put it in simple word. Hope you get it without much confusion - I read a man page for some command-switch/option which has a long description. I read it, ...
4
votes
1answer
72 views

unexpected output with grep

I am using pyrit. For those who dont know, pyrit allows among other things to check if a wpa handshake key is valid: pyrit -r file0.cap analyze when a file does not contain a valid key, here is ...
4
votes
3answers
574 views

Dynamically trim stdout line width in Bash

Lately, I have been experimenting with the ps command, and sometimes long paths wrap to the next line (or two) and make it hard to read. I want to pipe the ps output into another program to limit the ...
4
votes
4answers
189 views

How do I break up a file like split to stdout for piping to a command?

I have a large .sql file full of SELECT statements that contain data I want to insert into my SQL Server database. I'm looking for how I could basically take the file's contents, 100 lines at a time, ...
4
votes
1answer
575 views

Ksh loses data after piping 16K bytes

I recently found that ksh may lose some data after printing more than 16K bytes to the stdout if it is blocked for a couple of seconds. This test.sh script prints out 257*64 (16448) bytes: ...
4
votes
2answers
112 views

How to redirect stdout to a file and read from the same file simultaneously with another task?

I want to run a task (which takes quite a long time) remotely in Ubuntu Linux Bash via nohup and redirect stdout to a file, e.g.: nohup task > out.txt & From time to time I would like to ...
4
votes
1answer
176 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
3answers
166 views

Where does the output from an application started from the window manager go?

If you start an application from a terminal you can see the output to stdout and stderr, but if an application is started from the window manager, where does the output to these files typically go? To ...
4
votes
1answer
2k views

Writing to stdout except for output redirection C

I have to make a simple app for school. I have to write arguments one per line on the terminal, and return on stdout the user choices. For example, I write cat my_app main.c main.h, if the user ...
4
votes
1answer
128 views

Can redirecting stdout and stderr to the same file mangle lines?

I've read that when redirecting stdout and stderr to the same file using 2>&1, stdout is usually block buffered while stderr is unbuffered. If a very long line is written to stdout, requiring ...
4
votes
1answer
181 views

Discard stdout of a command for t seconds

I am working on some batch scripts involving the following: Run some non-terminating sub-processes (asynchronously) Wait for t seconds Perform other task X for some time Terminate subprocesses ...
3
votes
5answers
1k views

How to use filename arguments or default to stdin, stdout (brief)

I want to handle filenames as arguments in a bash script in a cleaner, more flexible way, taking 0, 1, or 2 arguments for input and output filenames. when args = 0, read from stdin, write to stdout ...
3
votes
2answers
77 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 > ...
3
votes
1answer
329 views

Shell script doesn't paint last line of stdout to screen without user input

I have a shell script that's happily doing all my backup process and writing progress to stderr and stdout, with one exception — the last line doesn't get written to my terminal (if I call the script ...
3
votes
2answers
216 views

Bash if script is called from terminal echo stdout to terminal, if from cron do not echo output

I would like to have a service watchdog script echo the status to the screen if called like ./watchdog.sh but if it is run by cron, there is no need to echo output. What is the proper method? Where ...