How to determine if a process exists using a shell script?

One way to determine if a process exists is by using the following method:

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if ps aux | grep -q "进程名"; then
    echo "进程存在"
else
    echo "进程不存在"
fi

1. display the process ID of a program

if pgrep "进程名" > /dev/null; then
    echo "进程存在"
else
    echo "进程不存在"
fi

Note: “process name” in the example above should be replaced with the actual process name.