How to trigger SIGUSR1 and SIGUSR2

Question

I m getting acquainted with signals in C  I can t figure out what kind of signals SIGUSR1 and SIGUSR2 are and how can I trigger them  Can anyone please explain it to me

User · Answer

terminal 1  dd if  dev sda of debian img   terminal 2    killall -SIGUSR1 dd   go back to terminal 1  34292201 0 records in 34292200 0 records out 17557606400 bytes  18 GB  copied  1034 7 s  17 0 MB s

User · Answer

They are signals that application developers use  The kernel shouldn t ever send these to a process  You can send them using kill 2  or using the utility kill 1    If you intend to use signals for synchronization you might want to check real-time signals  there s more of them  they are queued  their delivery order is guaranteed etc

User · Answer

They are user-defined signals  so they aren t triggered by any particular action   You can explicitly send them programmatically    include  lt signal h gt   kill pid  SIGUSR1     where pid is the process id of the receiving process   At the receiving end  you can register a signal handler for them    include  lt signal h gt   void my handler int signum        if  signum    SIGUSR1                printf  Received SIGUSR1  n             signal SIGUSR1  my handler

[c] How to trigger SIGUSR1 and SIGUSR2?

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