Shulou(Shulou.com)06/01 Report--

Brief introduction

Strace is often used to track system calls and received signals when a process is executing. In the Linux world, processes cannot access hardware devices directly. When processes need to access hardware devices (such as reading disk files, receiving network data, etc.), they must switch from user mode to kernel mode and access hardware devices through system calls. Strace can track system calls generated by a process, including parameters, return values, and execution time.

Output parameter meaning root@ubuntu:/usr# strace cat / dev/null execve ("/ bin/cat", ["cat", "/ dev/null"], [/ * 22 vars * /]) = 0brk (0) = 0xab1000access ("/ etc/ld.so.nohwcap", F_OK) =-1 ENOENT (No such file or directory) mmap (NULL, 8192, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS,-1 0) = 0x7f29379a7000access ("/ etc/ld.so.preload", R_OK) =-1 ENOENT (No such file or directory)... brk (0) = 0xab1000brk (0xad2000) = 0xad2000fstat (1, {st_mode=S_IFCHR | 0620, st_rdev=makedev (136,0),...}) = 0open ("/ dev/null", O_RDONLY) = 3fstat (3, {st_mode=S_IFCHR | 0666, st_rdev=makedev (1,3),...}) = 0read (3, "" 32768) = 0close (3) = 0close (1) = 0close (2) = 0exit_group (0) =?

Each line is a system call. To the left of the equal sign is the function name of the system call and its parameters, and on the right is the return value of the call.

Strace displays the parameters of these calls and returns values in symbolic form. Strace receives information from the kernel and does not need to build the kernel in any special way.

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