Trace a new process

Run a command under strace and save output to file

strace -o trace.log ls /tmp

More strace commands

Attach to running process

strace -p $(pgrep nginx | head -1) -o /tmp/nginx.trace

Trace syscalls of an already-running process by PID
Trace only specific syscalls

strace -e trace=openat,read,write curl https://example.com

Filter to file-related syscalls only
Count syscall statistics

strace -c -e trace=all python3 app.py

Summary table of syscall counts and time spent
Follow child processes

strace -f -e trace=process nginx -t

Trace syscalls in all forked children (-f)
Show timestamps

strace -tt -T curl https://example.com 2>&1 | head -40

-tt adds absolute time; -T shows time spent in each call