為什麼我在取消程序後仍會收到 stdout 或 stderr？

我啟動了 QEMU 並立即否認它，但仍然在我的 shell 上收到輸出：

aburk@aburk:~$ su
Password: 
[root@aburk aburk]# QEMU_AUDIO_DRV="pa" QEMU_PA_SERVER="/run/user/1000/pulse/native" qemu-system-x86_64 -m 3096M -hda /dev/sdb -cpu host -smp cores=3,threads=1,sockets=1 --enable-kvm
WARNING: Image format was not specified for '/dev/sdb' and probing guessed raw.
        Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
        Specify the 'raw' format explicitly to remove the restrictions.
^Z
[1]+  Stopped                 QEMU_AUDIO_DRV="pa" QEMU_PA_SERVER="/run/user/1000/pulse/native" qemu-system-x86_64 -m 3096M -hda /dev/sdb -cpu host -smp cores=3,threads=1,sockets=1 --enable-kvm
[root@aburk aburk]# bg
[1]+ QEMU_AUDIO_DRV="pa" QEMU_PA_SERVER="/run/user/1000/pulse/native" qemu-system-x86_64 -m 3096M -hda /dev/sdb -cpu host -smp cores=3,threads=1,sockets=1 --enable-kvm &
[root@aburk aburk]# 
(qemu-system-x86_64:19530): Gtk-WARNING **: Allocating size to GtkScrollbar 0x7f261f20c2c0 without calling gtk_widget_get_preferred_width/height(). How does the code know the size to allocate?

(qemu-system-x86_64:19530): Gtk-WARNING **: gtk_widget_size_allocate(): attempt to allocate widget with width -150829368 and height 400

(qemu-system-x86_64:19530): Gtk-WARNING **: Allocating size to GtkScrollbar 0x7f261f20c4c0 without calling gtk_widget_get_preferred_width/height(). How does the code know the size to allocate?

(qemu-system-x86_64:19530): Gtk-WARNING **: gtk_widget_size_allocate(): attempt to allocate widget with width -150829368 and height 400

(qemu-system-x86_64:19530): Gtk-WARNING **: Allocating size to GtkScrollbar 0x7f261f20c6c0 without calling gtk_widget_get_preferred_width/height(). How does the code know the size to allocate?

(qemu-system-x86_64:19530): Gtk-WARNING **: gtk_widget_size_allocate(): attempt to allocate widget with width -150829368 and height 400
jobs -p
19530
[root@aburk aburk]# disown 19530
[root@aburk aburk]# 
[root@aburk aburk]# 
[root@aburk aburk]# 
(qemu-system-x86_64:19530): Gtk-WARNING **: Allocating size to GtkScrollbar 0x7f261f20c2c0 without calling gtk_widget_get_preferred_width/height(). How does the code know the size to allocate?

(qemu-system-x86_64:19530): Gtk-WARNING **: gtk_widget_size_allocate(): attempt to allocate widget with width -150829368 and height 900

(qemu-system-x86_64:19530): Gtk-WARNING **: Allocating size to GtkScrollbar 0x7f261f20c4c0 without calling gtk_widget_get_preferred_width/height(). How does the code know the size to allocate?

(qemu-system-x86_64:19530): Gtk-WARNING **: gtk_widget_size_allocate(): attempt to allocate widget with width -150829368 and height 900

(qemu-system-x86_64:19530): Gtk-WARNING **: Allocating size to GtkScrollbar 0x7f261f20c6c0 without calling gtk_widget_get_preferred_width/height(). How does the code know the size to allocate?

(qemu-system-x86_64:19530): Gtk-WARNING **: gtk_widget_size_allocate(): attempt to allocate widget with width -150829368 and height 900

我可以通過在 View 菜單中調整 QEMU 的大小來手動觸發 GTK 警告。

我沒有正確地否認這個過程嗎？為什麼我仍然收到輸出？

我注意到，當我完全關閉我的 shell 並打開一個新的 shell 並 su 到 root 時，無論我多久調整一次 QEMU 的大小，我都不會收到任何這些消息。

我想知道這是如何工作的。

disown只從活動作業表中刪除一個作業（由 shell 維護），確保當 shell 終止時相應的程序不會被殺死。它不會改變程序的 I/O 設置（標準輸入、輸出和錯誤）；因此，disowned 作業的輸出仍然會發送到它開始的終端，或者它被重定向的任何地方。如果您關閉終端（假設輸出正在那裡），那麼輸出將失去，並且打開一個新的 shell 不會恢復輸出。在這種情況下，只要程序嘗試讀取或寫入終端，就會收到掛斷信號；有關詳細資訊，請參閱nohup、disown 和 & 之間的區別。

為了完全避免這個問題，您可以將程序的輸出重定向到/dev/null啟動它的時間。

引用自：https://unix.stackexchange.com/questions/379306