Questions tagged [coprocesses]
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17 questions
1
vote
1
answer
104
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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
1
vote
1
answer
263
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Bash coproc with python
I am playing with the coproc of Bash and I am failing to understand something.
I started with the following example:
Example#1
$ coproc MY_BASH { bash; }
[1] 95244
$ echo 'ls -l; echo EOD' >&&...
- 99
2
votes
1
answer
7k
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How does bash know about its parent's coprocess in this situation, and why does a shebang line change it?
outer.sh:
ls -l /proc/$$/exe
coproc cat
./inner.sh
kill $!
inner.sh:
ls -l /proc/$$/exe
set | grep COPROC || echo No match found
coproc cat
kill $!
When I run ./outer.sh, this gets printed:
...
0
votes
1
answer
682
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Return value vs return status of a coprocess
I don't understand this sentence about Coprocesses in the bash man page:
Since the coprocess is created as an asynchronous command, the coproc command always returns success. The return status of a ...
- 454
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0
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479
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zsh, zpty: How to read the output of a process after it has exited?
Start some command with zpty:
zpty -d x ; zpty x 'echo hi' ; sleep 1
How do I read its output now that it has exited?
zpty -r x
Returns 2, and this behavior seems expected per the manpage.
- 1,704
6
votes
2
answers
959
views
coproc and named pipe behaviour under command substitution
I have a requirement to make a function in a zsh shell script, that is called by command substitution, communicate state with subsequent calls to the same command substitution.
Something like C's ...
- 175
0
votes
1
answer
474
views
Using coprocess to write a name referenced variable in BASH
I currently try to start background process with coproc and update a name reference variable.
My not working code:
function updateVariable(){
local -n myVar="${1}"
#i=0;
while :
do
...
- 123
1
vote
0
answers
53
views
Usage of cvlc with coproc
I'm trying to feed to file descriptor .mp3 files the with the dummy interface of vlc, i.e., cvlc, in order to add to a playlist on the fly or override the entire file descriptor with new data (new ....
- 11
1
vote
1
answer
1k
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Coproc in bash script
I'm trying to do a simple shell script that will make my raspberry's bluetooth discoverable but i'm facing some issues. My raspberry is running Raspbian.
Running this through command line works ...
- 13
7
votes
2
answers
2k
views
Is it possible to have multiple concurrent coprocesses?
The intent of the test script1 below is to start an "outer" coprocess (running seq 3), read from this coprocess in a while-loop, and for each line read, print a line identifying the current iteration ...
- 16.4k
10
votes
4
answers
6k
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Run command in background with foreground terminal access
I am trying to create a function that can run an arbitrary command, interact with the child process (specifics omitted), and then wait for it to exit. If successful, typing run <command> will ...
- 2,087
1
vote
1
answer
531
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How does bash coprocess achieve its pipelining?
Note this passage from man bash ( emphasis mine ):
Coprocesses
A coprocess is a shell command preceded by the coproc reserved word. A
coprocess is executed asynchronously in a subshell, as if ...
- 16.9k
5
votes
2
answers
3k
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Is coproc <command> the same as <command> &? [duplicate]
I have read that $coproc < command > is different from $< command > & in that coproc will execute command in a sub-shell process.
But when I tested it, it worked just like $< ...
- 715
-3
votes
2
answers
538
views
inter process comunication in bash read commands in multiple background functions
I'm trying to get the following code to read from a main input then read that in one function then be able to send that into the input of another function but i am having trouble getting it to work ...
- 11
3
votes
1
answer
444
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Why does this gawk coprocess hang?
While having a go at Convert date in bash shell, I tried GNU awk's coprocess feature:
gawk -F, -v cmd='date +"%Y-%m-%d %H:%M:%S" -f-' '{print $5 |& cmd; cmd |& getline d; $5 = d}1' foo
This ...
- 77.9k