stapex(5)

1STAPEX(5)                     File Formats Manual                    STAPEX(5)
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NAME

6       stapex - systemtap examples
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LANGUAGE BASICS

11       These  examples  give  a  feel  for  basic systemtap syntax and control
12       structures.
13
14              global odds, evens
15
16              probe begin {
17                # "no" and "ne" are local integers
18                for (i=0; i<10; i++) {
19                  if (i % 2) odds [no++] = i
20                  else evens [ne++] = i
21                }
22                delete odds[2]
23                delete evens[3]
24                exit ()
25              }
26
27              probe end {
28                foreach (x+ in odds) {
29                  printf ("odds[%d] = %d0, x, odds[x])
30                }
31                foreach (x in evens-) {
32                  printf ("evens[%d] = %d0, x, evens[x])
33                }
34              }
35       This prints:
36              odds[1] = 1
37              odds[3] = 5
38              odds[4] = 7
39              odds[5] = 9
40              evens[5] = 8
41              evens[4] = 6
42              evens[2] = 2
43              evens[1] = 0
44       Note that all variables types are inferred, and  that  all  locals  and
45       globals are automatically initialized.
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48       This script prints the primes between 0 and 49.
49              function isprime (x) {
50                if (x < 2) return 0
51                for (i=2; i<x; i++) {
52                  if (x % i == 0) return 0
53                  if (i * i > x) break
54                }
55                return 1
56              }
57              probe begin {
58                for (i=0; i<50; i++)
59                  if (isprime (i)) printf("%d0, i)
60                exit()
61              }
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64       This script demonstrates recursive functions.
65              function fibonacci(i) {
66                if (i < 1) error ("bad number")
67                if (i == 1) return 1
68                if (i == 2) return 2
69                return fibonacci (i-1) + fibonacci (i-2)
70              }
71              probe begin {
72                printf ("11th fibonacci number: %d0, fibonacci (11))
73                exit ()
74              }
75       Any  larger  number  may exceed the MAXACTION or MAXNESTING limits, and
76       result in an error.
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PROBING

81       To trace entry and exit from a function, use a pair of probes:
82              probe kernel.function("sys_mkdir") { println ("enter") }
83              probe kernel.function("sys_mkdir").return { println ("exit") }
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85       To list the probeable functions in the kernel, use the last-pass option
86       to  the  translator.  That output needs to be filtered because each in‐
87       lined function instance is listed separately.
88              % stap -p2 -e 'probe kernel.function("*") {}' | sort | uniq
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NAME

LANGUAGE BASICS

PROBING

SEE ALSO