STAPEX(3stap) STAPEX(3stap)

# [NAME](#NAME)

stapex - systemtap examples

# [LANGUAGE BASICS](#LANGUAGE_BASICS)

These examples give a feel for basic systemtap syntax and control structures.

```
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)


  exit()
}
```

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](#PROBING)

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 mode.

```
% 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](#MORE_EXAMPLES)

The directory to find more examples can be found in the stappaths (7) manual page, and online at **http://sourceware.org/systemtap/examples/**

# [SEE ALSO](#SEE_ALSO)

```
stap(1)
stapprobes(3stap)
stappaths(7)
```

---

Document: stapex(3stap) from systemtap 5.6-r0 (Chainguard OS)
Source: https://sourceware.org/git/systemtap.git