It allows you to trace system calls made by a process. System calls are the fundamental interfaces between user space and the kernel.
Strace -f -p PID → -f for trace child thread
strace -c cmd or PID → print no of time each sys function get called and timing info
Note : Strace slow down the process
ltrace -> to see all library call
Using with htop
we can attach strace on running process sudo htop choose the process and press s it will attach the strace