Behavior of directly vs indirectly backgrounded children on read
Clash Royale CLAN TAG#URR8PPP
When I do
( sleep 1; read x ; echo x=$x; echo done ) &
then with the default terminal settings, the job gets stopped by SIGTTIN.
If I do
( ( sleep 1; read x ; echo x=$x; echo done ) & )
the read syscall inside read gets EOF (returns with 0)` and no stopping by SITTIN happens.
What is the explanation for these behavior
shell terminal signals job-control
asked Jan 30 at 20:23
PSkocikPSkocik
18k54996
add a comment |
When I do
( sleep 1; read x ; echo x=$x; echo done ) &
then with the default terminal settings, the job gets stopped by SIGTTIN.
If I do
( ( sleep 1; read x ; echo x=$x; echo done ) & )
the read syscall inside read gets EOF (returns with 0)` and no stopping by SITTIN happens.
What is the explanation for these behavior
shell terminal signals job-control
asked Jan 30 at 20:23
PSkocikPSkocik
18k54996
add a comment |
When I do
( sleep 1; read x ; echo x=$x; echo done ) &
then with the default terminal settings, the job gets stopped by SIGTTIN.
If I do
( ( sleep 1; read x ; echo x=$x; echo done ) & )
the read syscall inside read gets EOF (returns with 0)` and no stopping by SITTIN happens.
What is the explanation for these behavior
shell terminal signals job-control
asked Jan 30 at 20:23
PSkocikPSkocik
18k54996
When I do
( sleep 1; read x ; echo x=$x; echo done ) &
then with the default terminal settings, the job gets stopped by SIGTTIN.
If I do
( ( sleep 1; read x ; echo x=$x; echo done ) & )
the read syscall inside read gets EOF (returns with 0)` and no stopping by SITTIN happens.
What is the explanation for these behavior
shell terminal signals job-control
shell terminal signals job-control
asked Jan 30 at 20:23
PSkocikPSkocik
18k54996
asked Jan 30 at 20:23
PSkocikPSkocik
18k54996
asked Jan 30 at 20:23
PSkocikPSkocik
18k54996
asked Jan 30 at 20:23
PSkocikPSkocik
18k54996
asked Jan 30 at 20:23
PSkocikPSkocik
18k54996
18k54996
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
That's because in the second case the backgrounded command will be run in a subshell, and as there's no job control in subshells, the background mode will be faked by redirecting the input from /dev/null and ignoring the SIGINT and SIGQUIT signals.
See also these answers:
Background process of subshell strange behaviour
Process started by script does not receive SIGINT
Does ` (sleep 123 &)` remove the process group from bash's job control?
Process killed before being launched in background
answered Jan 30 at 20:57
mosvymosvy
7,6421530
add a comment |
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1 Answer
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1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
That's because in the second case the backgrounded command will be run in a subshell, and as there's no job control in subshells, the background mode will be faked by redirecting the input from /dev/null and ignoring the SIGINT and SIGQUIT signals.
See also these answers:
Background process of subshell strange behaviour
Process started by script does not receive SIGINT
Does ` (sleep 123 &)` remove the process group from bash's job control?
Process killed before being launched in background
answered Jan 30 at 20:57
mosvymosvy
7,6421530
add a comment |
That's because in the second case the backgrounded command will be run in a subshell, and as there's no job control in subshells, the background mode will be faked by redirecting the input from /dev/null and ignoring the SIGINT and SIGQUIT signals.
See also these answers:
Background process of subshell strange behaviour
Process started by script does not receive SIGINT
Does ` (sleep 123 &)` remove the process group from bash's job control?
Process killed before being launched in background
answered Jan 30 at 20:57
mosvymosvy
7,6421530
add a comment |
That's because in the second case the backgrounded command will be run in a subshell, and as there's no job control in subshells, the background mode will be faked by redirecting the input from /dev/null and ignoring the SIGINT and SIGQUIT signals.
See also these answers:
Background process of subshell strange behaviour
Process started by script does not receive SIGINT
Does ` (sleep 123 &)` remove the process group from bash's job control?
Process killed before being launched in background
answered Jan 30 at 20:57
mosvymosvy
7,6421530
That's because in the second case the backgrounded command will be run in a subshell, and as there's no job control in subshells, the background mode will be faked by redirecting the input from /dev/null and ignoring the SIGINT and SIGQUIT signals.
See also these answers:
Background process of subshell strange behaviour
Process started by script does not receive SIGINT
Does ` (sleep 123 &)` remove the process group from bash's job control?
Process killed before being launched in background
answered Jan 30 at 20:57
mosvymosvy
7,6421530
edited Jan 31 at 23:32
answered Jan 30 at 20:57
mosvymosvy
7,6421530
answered Jan 30 at 20:57
mosvymosvy
7,6421530
answered Jan 30 at 20:57
mosvymosvy
7,6421530
7,6421530
add a comment |
add a comment |
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