Attach to running process

Trace syscalls of an already-running process by PID

strace -p $(pgrep nginx | head -1) -o /tmp/nginx.trace
tool
strace13 commands
tags
stracelinuxdebug

More strace commands

  • 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

  • Trace file access
    strace -e trace=openat -e trace=file myapp 2>&1 | grep 'ENOENT'

    Find files the process tries to open but cannot find

all 13 strace commands