Shulou(Shulou.com)06/03 Report--

A signal is a soft interrupt, a way to handle asynchronous events. Generally speaking, the operating system supports many signals. In UNIX, in particular, more important applications generally process signals.

UNIX defines many signals, such as SIGINT for interrupt character signal, that is, Ctrl+C signal, SIGBUS for hardware failure signal, SIGCHLD for subprocess state change signal, SIGKILL for signal to terminate program running, and so on. Semaphore programming is a very important technology in UNIX.

Unix semaphores can also be viewed in the file / usr/include/sys/signal.h

# define SIGHUP process because the control terminal dies or the control terminal issues a command

# signal generated by interruption of define SIGINT keyboard

# define SIGQUIT Keyboard termination

# illegal define SIGILL instruction

# the define SIGTRAP process encounters a trace or an interrupt nesting

# define SIGABRT interrupt signal generated by abort system call

# define SIGIOT is similar to SIGABRT

# define SIGBUS process attempts to use unreasonable memory

# define SIGFPE floating point exception

# define SIGKILL KILL

# define SIGUSR1 user customization

# define SIGSEGV segment error

# define SIGUSR2 user customization

# define SIGPIPE pipeline operation without read-only write

# define SIGALRM timer clock signal generated by alarm system call

# define SIGTERM process of receiving terminal signal

# define SIGSTKFLT stacking error

# the define SIGCHLD child process signals to the parent that the child process has been stop or terminated

# signal that define SIGCONT continues to run

# define SIGSTOP stop

# stop signal generated by define SIGTSTP keyboard

# define SIGTTIN needs to read stdin data when running in a later state

# define SIGTTOU needs to write to stdout when running in a later state

# Emergency of define SIGURG socket

# the time allocated by the define SIGXCPU process to overuse CPU

# the define SIGXFSZ process uses files that exceed the file length specified by the system

# alarm clock inside define SIGVTALRM expires

# define SIGPROF depicts clock set expiration in a program segment

# changes to the define SIGWINCH terminal window

# define SIGIO Asynchronous IO

# define SIGPOLL SIGIO pollable event occurs

By using: trap with the trap command

The above knowledge of Unix semaphores, I hope you can remember, to facilitate our future use.

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