Questions tagged [file-descriptors]
The file-descriptors tag has no summary.
400 questions
4
votes
1
answer
808
views
Why does bash need file descriptor duplicating?
I found out I don't totally understand how bash file descriptors work. I would like to have some guidance here.
I have a scenario where I need to read the content of a file, and for each line of the ...
- 718
1
vote
1
answer
102
views
coproc redirect to stdout
Suppose I have some process that when ready will output to stdout. Even though I want my script to run asynchronously with respect to that process, I still want the script to block and wait on that ...
- 273
5
votes
2
answers
425
views
How (internally) does fd3>&fd1 after { fd1>&fd3 } put back (or not) original fd into fd1? ("bad file descriptor")
`I'm reading an answer to https://stackoverflow.com/questions/692000/how-do-i-write-standard-error-to-a-file-while-using-tee-with-a-pipe/692009#692009, https://stackoverflow.com/a/14737103/5499118:
{ {...
- 1,287
3
votes
1
answer
174
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Bash redirections - handling several filenames specially (man pages)
Please confirm/correct me. I've found related Duplication of file descriptors in redirection but that does not answer my specific question.
From the The GNU Bash Reference Manual, section 3.6 ...
- 1,483
0
votes
0
answers
62
views
I want to print debug output on failure, but ERR trap doesn't fire
I want to only print the debug output on failure, this is my attempt:
#!/bin/bash
set -euo pipefail
dt-api() {
# shellcheck disable=SC2086
curl \
--fail-with-body \
--silent \
...
- 325
0
votes
1
answer
99
views
What is (if any) the file descriptor of /dev/tty?
The urgent issue to read keyboard input in the pipeline is solved by the answer in https://stackoverflow.com/questions/15230289/read-keyboard-input-within-a-pipelined-read-loop:
mycommand-outputpiped |...
- 1,483
2
votes
2
answers
507
views
what is the meaning and usage of 2>&1 | tee /dev/stderr
for the following command
output=$(cat $file | docker exec -i CONTAINER COMMAND 2>&1 | tee /dev/stderr)
what is the meaning and usage of 2>&1 | tee /dev/stderr?
I google and 2>&...
- 133
7
votes
1
answer
1k
views
Why does MacOS always append to a redirected file descriptor even when told to overwrite? Ubuntu only appends when strictly told to append
Given the following code:
out="$(mktemp)"
rm -f "$out"
clear
printf '%s\n' 0 >"$out"
{
printf '%s\n' '1' >/dev/stdout
printf '%s\n' '2' >/dev/stdout
} &...
- 644
1
vote
0
answers
81
views
How to solve uninterruptible sleep process deadlock without reboot
I have a process stuck in uninterruptible sleep.
The problematic syscall is a read syscall towards /dev/fd0, which is not backed by a real floppy drive.
I am trying to use modprobe and rmmod (both ...
1
vote
1
answer
93
views
Are file permissions copied into the Open File Table?
I have a doubt on what the entry created in the Open File Table upon calling open() contains.
The following schema
from bytebytego seems quite good to understand the big picture of opening a file, ...
- 113
1
vote
1
answer
243
views
bash: script running in pm2 unable to access file descriptors files at /dev/fd/
I have script script.sh:
#!/usr/bin/env bash
# pm2 seems to always run in `bash` regardless of `#!`
echo "running in $(readlink -f /proc/$$/exe)"
# Redirect to both stdout(1) and stderr(2)
...
- 313
2
votes
1
answer
350
views
Shell/bash: Can I create a file descriptor to an existing file without emptying the file? [duplicate]
Context: I have cursory bash experience. I do not fully get file descriptors, just some basic usage. Trying to create a setup script. Most done, but a few "kinks" remain.
So here is a newbie ...
- 23
0
votes
0
answers
30
views
How to bypass pipe detection? [duplicate]
A question at stackoverflow has answers that show the following way of detecting if standard output is a pipe:
if [ -t 1 ] ; then echo terminal; else echo "not a terminal"; fi
The -t flag ...
- 428
1
vote
0
answers
121
views
Is there a known linux kernel bug with two threads incorrectly getting back the same file descriptor number?
I've got a multithreaded program in which a sem_open with O_CREAT occasionally fails with EBADF. This is on an ARM linux 4.9.88, from NXP, on an embedded device.
It is very difficult to reproduce, ...
- 111
1
vote
1
answer
837
views
Capturing output from a bash function without using a subshell [closed]
I have a bash script listening on a pipe for commands. When it sees a command it runs it. However, I would like it to support the "sideloading" of bash functions that can be called at a ...
- 9,379