GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
CentOS 5.1 |
|
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stapex(5) |
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stapex − systemtap examples
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] = %d0, x, odds[x])
}
foreach (x in evens−) {
printf ("evens[%d] = %d0, 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("%d0, 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: %d0, fibonacci (11))
exit ()
}
Any larger number may exceed the MAXACTION or MAXNESTING limits, and result in an error.
To trace entry and exit from a function, use a pair of probes:
probe
kernel.function("sys_mkdir") { log
("enter") }
probe kernel.function("sys_mkdir").return { log
("exit") }
To list the probeable functions in the kernel, use the last-pass option to the translator. That output needs to be filtered because each inlined function instance is listed separately.
% stap −p2 −e 'probe kernel.function("*") {}' | sort | uniq
/usr/doc/systemtap*/examples stap(1) stapprobes(5) stapfuncs(5)
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stapex(5) | |