PERLCLIB(1) Perl Programmers Reference Guide PERLCLIB(1)
NAME
perlclib - Internal replacements for standard C library functions
DESCRIPTION
One thing Perl porters should note is that perl doesnt tend to use
that much of the C standard library internally; youll see very little
use of, for example, the ctype.h functions in there. This is because
Perl tends to reimplement or abstract standard library functions, so
that we know exactly how theyre going to operate.
This is a reference card for people who are familiar with the C library
and who want to do things the Perl way; to tell them which functions
they ought to use instead of the more normal C functions.
Conventions
In the following tables:
"t"
is a type.
"p"
is a pointer.
"n"
is a number.
"s"
is a string.
"sv", "av", "hv", etc. represent variables of their respective types.
File Operations
Instead of the stdio.h functions, you should use the Perl abstraction
layer. Instead of "FILE*" types, you need to be handling "PerlIO*"
types. Dont forget that with the new PerlIO layered I/O abstraction
"FILE*" types may not even be available. See also the "perlapio" docu
mentation for more information about the following functions:
Instead Of: Use:
stdin PerlIO_stdin()
stdout PerlIO_stdout()
stderr PerlIO_stderr()
fopen(fn, mode) PerlIO_open(fn, mode)
freopen(fn, mode, stream) PerlIO_reopen(fn, mode, perlio) (Deprecated)
fflush(stream) PerlIO_flush(perlio)
fclose(stream) PerlIO_close(perlio)
File Input and Output
Instead Of: Use:
fprintf(stream, fmt, ...) PerlIO_printf(perlio, fmt, ...)
[f]getc(stream) PerlIO_getc(perlio)
[f]putc(stream, n) PerlIO_putc(perlio, n)
ungetc(n, stream) PerlIO_ungetc(perlio, n)
Note that the PerlIO equivalents of "fread" and "fwrite" are slightly
different from their C library counterparts:
fread(p, size, n, stream) PerlIO_read(perlio, buf, numbytes)
fwrite(p, size, n, stream) PerlIO_write(perlio, buf, numbytes)
fputs(s, stream) PerlIO_puts(perlio, s)
There is no equivalent to "fgets"; one should use "sv_gets" instead:
fgets(s, n, stream) sv_gets(sv, perlio, append)
File Positioning
Instead Of: Use:
feof(stream) PerlIO_eof(perlio)
fseek(stream, n, whence) PerlIO_seek(perlio, n, whence)
rewind(stream) PerlIO_rewind(perlio)
fgetpos(stream, p) PerlIO_getpos(perlio, sv)
fsetpos(stream, p) PerlIO_setpos(perlio, sv)
ferror(stream) PerlIO_error(perlio)
clearerr(stream) PerlIO_clearerr(perlio)
Memory Management and String Handling
Instead Of: Use:
t* p = malloc(n) Newx(id, p, n, t)
t* p = calloc(n, s) Newxz(id, p, n, t)
p = realloc(p, n) Renew(p, n, t)
memcpy(dst, src, n) Copy(src, dst, n, t)
memmove(dst, src, n) Move(src, dst, n, t)
memcpy/*(struct foo *) StructCopy(src, dst, t)
memset(dst, 0, n * sizeof(t)) Zero(dst, n, t)
memzero(dst, 0) Zero(dst, n, char)
free(p) Safefree(p)
strdup(p) savepv(p)
strndup(p, n) savepvn(p, n) (Hey, strndup doesnt exist!)
strstr(big, little) instr(big, little)
strcmp(s1, s2) strLE(s1, s2) / strEQ(s1, s2) / strGT(s1,s2)
strncmp(s1, s2, n) strnNE(s1, s2, n) / strnEQ(s1, s2, n)
Notice the different order of arguments to "Copy" and "Move" than used
in "memcpy" and "memmove".
Most of the time, though, youll want to be dealing with SVs internally
instead of raw "char *" strings:
strlen(s) sv_len(sv)
strcpy(dt, src) sv_setpv(sv, s)
strncpy(dt, src, n) sv_setpvn(sv, s, n)
strcat(dt, src) sv_catpv(sv, s)
strncat(dt, src) sv_catpvn(sv, s)
sprintf(s, fmt, ...) sv_setpvf(sv, fmt, ...)
Note also the existence of "sv_catpvf" and "sv_vcatpvfn", combining
concatenation with formatting.
Sometimes instead of zeroing the allocated heap by using Newxz() you
should consider "poisoning" the data. This means writing a bit pattern
into it that should be illegal as pointers (and floating point num
bers), and also hopefully surprising enough as integers, so that any
code attempting to use the data without forethought will break sooner
rather than later. Poisoning can be done using the Poison() macro,
which has similar arguments as Zero():
Poison(dst, n, t)
Character Class Tests
There are two types of character class tests that Perl implements: one
type deals in "char"s and are thus not Unicode aware (and hence depre
cated unless you know you should use them) and the other type deal in
"UV"s and know about Unicode properties. In the following table, "c" is
a "char", and "u" is a Unicode codepoint.
Instead Of: Use: But better use:
isalnum(c) isALNUM(c) isALNUM_uni(u)
isalpha(c) isALPHA(c) isALPHA_uni(u)
iscntrl(c) isCNTRL(c) isCNTRL_uni(u)
isdigit(c) isDIGIT(c) isDIGIT_uni(u)
isgraph(c) isGRAPH(c) isGRAPH_uni(u)
islower(c) isLOWER(c) isLOWER_uni(u)
isprint(c) isPRINT(c) isPRINT_uni(u)
ispunct(c) isPUNCT(c) isPUNCT_uni(u)
isspace(c) isSPACE(c) isSPACE_uni(u)
isupper(c) isUPPER(c) isUPPER_uni(u)
isxdigit(c) isXDIGIT(c) isXDIGIT_uni(u)
tolower(c) toLOWER(c) toLOWER_uni(u)
toupper(c) toUPPER(c) toUPPER_uni(u)
stdlib.h functions
Instead Of: Use:
atof(s) Atof(s)
atol(s) Atol(s)
strtod(s, *p) Nothing. Just dont use it.
strtol(s, *p, n) Strtol(s, *p, n)
strtoul(s, *p, n) Strtoul(s, *p, n)
Notice also the "grok_bin", "grok_hex", and "grok_oct" functions in
numeric.c for converting strings representing numbers in the respective
bases into "NV"s.
In theory "Strtol" and "Strtoul" may not be defined if the machine perl
is built on doesnt actually have strtol and strtoul. But as those 2
functions are part of the 1989 ANSI C spec we suspect youll find them
everywhere by now.
int rand() double Drand01()
srand(n) { seedDrand01((Rand_seed_t)n);
PL_srand_called = TRUE; }
exit(n) my_exit(n)
system(s) Dont. Look at pp_system or use my_popen
getenv(s) PerlEnv_getenv(s)
setenv(s, val) my_putenv(s, val)
Miscellaneous functions
You should not even want to use setjmp.h functions, but if you think
you do, use the "JMPENV" stack in scope.h instead.
For "signal"/"sigaction", use "rsignal(signo, handler)".
SEE ALSO
"perlapi", "perlapio", "perlguts"
perl v5.8.8 2008-04-25 PERLCLIB(1)
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