stapex(3stap) — Linux manual page


STAPEX(3stap)                                              STAPEX(3stap)

NAME         top

       stapex - systemtap examples


       These examples give a feel for basic systemtap syntax and control

              global odds, evens

              probe begin {
                # "no" and "ne" are local integers
                for (i=0; i<10; i++) {
                  if (i % 2) odds [no++] = i
                  else evens [ne++] = i
                delete odds[2]
                delete evens[3]
                exit ()

              probe end {
                foreach (x+ in odds) {
                  printf ("odds[%d] = %d\n", x, odds[x])
                foreach (x in evens-) {
                  printf ("evens[%d] = %d\n", x, evens[x])

       This prints:

              odds[1] = 1
              odds[3] = 5
              odds[4] = 7
              odds[5] = 9
              evens[5] = 8
              evens[4] = 6
              evens[2] = 2
              evens[1] = 0

       Note that all variables types are inferred, and that all locals
       and globals are automatically initialized.

       This script prints the primes between 0 and 49.

              function isprime (x) {
                if (x < 2) return 0
                for (i=2; i<x; i++) {
                  if (x % i == 0) return 0
                  if (i * i > x) break
                return 1
              probe begin {
                for (i=0; i<50; i++)
                  if (isprime (i)) printf("%d\n", i)

       This script demonstrates recursive functions.

              function fibonacci(i) {
                if (i < 1) error ("bad number")
                if (i == 1) return 1
                if (i == 2) return 2
                return fibonacci (i-1) + fibonacci (i-2)
              probe begin {
                printf ("11th fibonacci number: %d\n", fibonacci (11))
                exit ()

       Any larger number may exceed the MAXACTION or MAXNESTING limits,
       and result in an error.

PROBING         top

       To trace entry and exit from a function, use a pair of probes:

              probe kernel.function("sys_mkdir") { println ("enter") }
              probe kernel.function("sys_mkdir").return { println ("exit") }

       To list the probeable functions in the kernel, use the listings

              % stap -l 'kernel.function("*")'

       To list the probeable functions and local variables in the
       kernel, use another listings mode.

              % stap -L 'kernel.function("*")'

MORE EXAMPLES         top

       The directory to find more examples can be found in the stappaths
       (7) manual page, and online at 

SEE ALSO         top


COLOPHON         top

       This page is part of the systemtap (a tracing and live-system
       analysis tool) project.  Information about the project can be
       found at ⟨⟩.  If you have a bug
       report for this manual page, send it to
       This page was obtained from the project's upstream Git repository
       ⟨git://⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-21.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to


Pages that refer to this page: stap(1)stap-merge(1)stappaths(7)stapbpf(8)stapdyn(8)staprun(8)stap-server(8)