Linked Questions

5
votes
3answers
370 views

Why does this one-liner fail to produce output? [duplicate]

The following produces nothing in bash: while true ; do upower -d ; sleep 1 ; done | grep percentage | uniq I've discovered that it doesn't matter what the last- or even the second to last- program ...
1
vote
1answer
241 views

Flush data to file frequently for long running command? [duplicate]

I have a command that processes data slowly. The command processes lines from a file and writes the results to the output file data.txt: my_command > data.txt The issue I have is that I'd like to ...
0
votes
1answer
218 views

Using tee or pipe to log console output will cause my program not to start [duplicate]

I'm running hostapd on my raspberry PI to let it function as an accesspoint. It's working fine with the following command: sudo hostapd /etc/hostapd/hostapd.conf This will start hostapd and log all ...
1
vote
1answer
91 views

strange behaviour of strings command [duplicate]

I am trying to capture mysql traffic and pass those traffic to strings command as follows: tcpdump -i any -s 0 -l -w - dst port 3306 | strings This is working as expected and printing all mysql ...
0
votes
1answer
58 views

Why doesn't this simple piping with awk work? [duplicate]

I'm trying to follow this answer but I can't make it work. I simplified it down as much as I could to try work out what's going on (just running this at the terminal for now): rsync --progress -iav ...
53
votes
4answers
51k views

How big is the pipe buffer?

As a comment in I'm confused as to why "| true" in a makefile has the same effect as "|| true" user cjm wrote: Another reason to avoid | true is that if the command ...
9
votes
4answers
1k views

Stopping output from a program run in SSH session NOW

Problem I execute command that outputs LOTS of information through SSH. For example, I foolishly add debug information inside a loop that executes million times, or just run cat /dev/urandom for ...
12
votes
2answers
1k views

“tail -f | iconv -fsjis” does not output anything

I want to tail -f a file, but its content is in sjis encoding, so I need to have it converted to the native (utf-8) encoding of my terminal. When I do tail -f x | iconv -fsjis there will be no ...
3
votes
3answers
998 views

Can't process stdout with pipe as it comes

I'm running tshark on a fifo, and the following is a bare example of a loop that prints the output of tshark as it comes: tshark -i $fifo | while read line; do echo $line done The problem ...
4
votes
1answer
3k views

Flush 'tail -f' buffer?

I'm using the following statement (simplified version): tail -f -c+1 <filename> in order to pipe a file to a process. What I've found, though, is that there is a number of lines at the end ...
6
votes
4answers
636 views

How to grep netcat output

I'm trying to grep live text stream from netcat, but it doesn't work for me: netcat localhost 9090 | grep sender returns nothing, but I'm sure that it should. If I redirect the netcat output to a ...
7
votes
1answer
4k views

Why does redirection (>) not work sometimes but appending (>>) does?

While studying for the RHCE, I came across a situation where stdin redirection does not work in bash: # file /tmp/users.txt /tmp/users.txt: cannot open `/tmp/users.txt' (No such file or directory) ...
3
votes
2answers
754 views

Read data from a pipe for a certain amount of time (in seconds)

Is there an easy way to create a pipe that only lasts for a given amount of wall time? I want to be able to take a "snapshot" of what's being written STDOUT for a period of time (rather than bytes or ...
8
votes
2answers
239 views

How bash treats “> >()”

While experimenting with output redirection and process substitution I stumbled upon the following command and its resulting output: me@elem:~$ echo foo > >(cat); echo bar bar me@elem:~$ ...

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