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操作系统Interprocess Communication（IPC）实验源码。 在Unix的内核环境中

compile:
	gcc -o semtool semtool.c
run:
./semtool c 5
Attempting to create new semaphore set with 5 members

ipcs -s
------ Semaphore Arrays --------
key        semid      owner      perms      nsems      status      
0x73078101 32768      root      666        5         

./semtool l 1
get member count 5
Semaphore resources decremented by one (locked)
semval for member 1 is 0

./semtool u 1
Semaphore resources incremented by one (unlocked)
semval for member 1 is 1

./semtool m 660
Old permissions were 666
Updated...

ipcs -s
------ Semaphore Arrays --------
key        semid      owner      perms      nsems      status      
0x73078101 32768      root      660        5         

./semtool d
Semaphore removed

ipcs -s
------ Semaphore Arrays --------
key        semid      owner      perms      nsems      status