Seeing all the system calls that were made by a Java program

Question

How can I see which system calls my Java program is making? Is there a tool that will do this on Linux?

Answer 1

Use strace:

strace -f java your_program

or

strace -f -p <pid of your java program>

Answer 2

Use strace. But there is is trick for my case. Option -f is needed and is the same as --follow-forks. For example, the following code:

public class Foo {
    public static void main (String [] args) {
        System.out.println("XXX");    
    }
}

After running javac Foo.java to compile it, strace java Foo 2>&1 | grep write print nothing. But strace -f java Foo 2>&1 | grep write prints:

[pid 11655] write(3, "0x63", 4)         = 4
[pid 11655] write(3, "\0", 1)           = 1
[pid 11655] write(3, "\0", 1)           = 1
[pid 11655] write(3, "\0", 1)           = 1
[pid 11655] write(3, "\0", 1)           = 1
[pid 11655] write(3, "\0", 1)           = 1
[pid 11655] write(3, "\0", 1)           = 1
[pid 11655] write(3, "\0", 1)           = 1
[pid 11655] write(3, "\0", 1)           = 1
[pid 11655] write(1, "XXX", 3XXX)          = 3
[pid 11655] write(1, "\n", 1

[pid 11655] write(1, "XXX", 3XXX) = 3 shows the system call made for System.out.println("XXX").