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2
votes
2answers
417 views

stop pipe() opening stdin

I've currently got code that forks two processes. The first reads a http streaming radio and pushes the data down a pipe (opened with pipe() ) for the second process to read, decode and output to the ...
2
votes
2answers
311 views

Any way in Bash to write to a file every X seconds without closing it?

The hardware watchdog on my system needs a 0 written to /dev/watchdog at less than 60 seconds interval or it will fire. The file handle must be kept open however or the watchdog is then disabled. ...
2
votes
4answers
109 views

Can a running script identify the logging context?

Let us say I redirect the STDOUT, STDERR of a program to files. ./script.sh 1> output.log 2> error.log Can the running program find this out i.e. know the paths to these files?
2
votes
2answers
179 views

Redirecting only stderr to a pipe

This code snippet is from Advanced Bash Scripting Guide. # Redirecting only stderr to a pipe. exec 3>&1 # Save current "value" of stdout. ls -l 2>&1 ...
2
votes
1answer
163 views

Why is it possible to refer to a closed stderr under bash?

I'd like to know why bash doesn't display an error message when we refer to a closed stderr. When it comes to other file descriptors, they have to be opened if we want to, for example, duplicate them. ...
2
votes
2answers
174 views

Where to place a Bash shell redirection for a command? [duplicate]

Possible Duplicate: Order of redirections Apart from the standalone exec >&2 to redirect the current shell's input and output are there any behavioral differences in the following ...
2
votes
1answer
21 views

Forcing write(2) to return 0

I am writing unit tests and would like to test some code's handling of the case where a call to write(2) returns zero. As ever, it would be nice to keep the test as authentic as possible. I can use a ...
2
votes
1answer
305 views

closing the unwanted file descriptors

I am trying to understand how pipes work . This code snippet is from some website . So my understanding of the program goes like this : When we do pipe(fd) then fd[0]=3 and fd[0]=4 ( assuming only ...
2
votes
1answer
324 views

Why doesnt ctrl+d work with this?

I wanted a simple way to process text in my clipboard without having to create a file. I tried using the following line: awk '{print $1}' <(cat) but I couldn't send cat the EOF character using ...
2
votes
2answers
477 views

AIX open() : file descriptor is zero (!?)

A daemon process, on detecting the presence of a text file in a particular directory then launches an executable file which opens the aforementioned text file in order to read and then transmit its ...
2
votes
1answer
361 views

open() console for default file descriptors

I'm reading a shell program implementation in C ( the xv6 shell from MIT's 6.828 Operating System Engineering course ). The main() function for this shell starts with the following code: //Assumes ...
2
votes
1answer
69 views

How is the inherited file descritor vulnerability dealt with in Unices?

Ulrich Drepper describes a vulnerability in programs that have open file descriptors then they fork() and execve() without lots of very careful locking in place. He also talks about new kernel ...
2
votes
1answer
159 views

Max Open Files, clarification needed

On my machine, ulimit -n returns 2560 Given that -n returns The maximum number of open file descriptors. Does it mean that system won't allow more then 2560 open files to be out there at any ...
2
votes
1answer
56 views

Is there a system call to bind a file descriptor directly into another?

A read() & write() loop would probably be as good as what I'm looking for, but nevertheless is anything like that around or is it impossible because of an obstacle I didn't envisage ? I'm curious
2
votes
0answers
17 views

Is it safe to create a regression test that relies on running out of file descriptor limit?

I'm writing a regression test for my modification of Nmap and I'm wondering if it's a good idea to create a test that would basically perform a large-scale connect() scan on 127.0.0.1/8, which would ...
1
vote
2answers
142 views

Process substitution with input redirection

I am trying to understand input redirection in combination with process substituation. I am using bash 3 An example with tr is the following $ tr "o" "a" <(echo "Foo") tr: extra operand ...
1
vote
3answers
2k views

How to check which process is using a given file descriptor?

Somewhere in the middle of my application, the framework I'm using (ROOT) gives me the following error: *** Break *** write on a pipe with no one to read it SysError in ...
1
vote
1answer
550 views

Understand file descriptors and nodejs

I'm having a bit of a confused time understanding what a file descriptor is and if I even need one! I am trying to spawn a process in nodejs and have its out put be written directly to an out put ...
1
vote
2answers
61 views

What fd's are used when doing diff <(cat old) <(cat new)?

If I do: diff <(cat old) <(cat new) Hoe does that work internally for the diff program? And how I do the same trick with a bash script?
1
vote
2answers
34 views

Map reading/writing a file to getting output from/sending input to a script?

Suppose I have two scripts, script1.sh and script2.sh. I am wondering if there is a way to make a filesystem interface such that, for example, I can go vim file and then have my system run script1.sh ...
1
vote
0answers
13 views

Capturing data from a Fluke 1620a via Bash /dev/tcp file descriptor

I am currently trying to develop a script that will connect to a Fluke DewK 1620a Themo-Hygrometer and pull the current temperature and humidity readings from the device. While these devices have a ...
1
vote
0answers
33 views

open() sys call [closed]

Process A wants to open a file fd1 = open("/var/file1", O_RDONLY); In the process of opening file1 which table is referred first system wide file table or file descriptor table or in-core inode ...
1
vote
0answers
234 views

Which socket is gnome-shell reading from continuously?

strace shows that the GNOME shell is continuously trying to read from a socket, which is often not available (or doesn't contain any data to read from): strace -p gnome-shell-pid -e trace=recvfrom ...
0
votes
2answers
240 views

Why doesn't Bash accept `&>&3`, i.e. redirecting stdout and stderr to file descriptor 3?

Given the preamble, foobar function and invocations of it: exec 3>/dev/null function foobar { echo foo; echo bar >&2; } foobar >/dev/null foobar 2>/dev/null foobar ...
0
votes
2answers
256 views

How to reset the file descriptor

I was trying to use file descriptor for printing the lines in the file #!/usr/bin/ksh exec 3<&0 exec 0< file.txt while read LINE do echo “$LINE” done and I am done with my code ,it ...
0
votes
1answer
40 views

How to find file/device given the resource ID on Linux?

On a gentoo Linux system I am printing the value of a file descriptor from within a PHP script yielding the following output: Resource id #1234 How to find the corresponding file/device given this ...