Author: Surendra Anne

The strace command is useful for debugging any command or a script. Thachievedheived by using a concept called command on command. The strace command has some other sister commands like ps, pstree, lsof etc. What is Linux strace command do? The primary purpose of the strace command is to show system calls which are created by the kernel when working with some process. Say suppose you write a program and want to see how it interacts with the system when it is executed, strace is your friend. The strace command is just a light debugger for your programs and command. In below example, we tried to run the pwd command and showed you what steps will be taken place. Syntax of strace command strace <command> Example: root@linuxnix:~# strace pwd execve("/bin/pwd", ["pwd"], [/* 73 vars */]) = 0 brk(NULL) = 0x148c000 access("/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) = 0x7f5f89746000 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3 fstat(3, {st_mode=S_IFREG|0644, st_size=162567, ...}) = 0 mmap(NULL, 162567, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f5f8971e000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3 read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0P\t\2\0\0\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0755, st_size=1868984, ...}) = 0 mmap(NULL, 3971488, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f5f89159000 mprotect(0x7f5f89319000, 2097152, PROT_NONE) = 0 mmap(0x7f5f89519000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1c0000) = 0x7f5f89519000...