=head1 NAME
perlclib - Internal replacements for standard C library functions
=head1 DESCRIPTION
One thing Perl porters should note is that F<perl> doesn't tend to use that
much of the C standard library internally; you'll see very little use of,
for example, the F<ctype.h> functions in there. This is because Perl
tends to reimplement or abstract standard library functions, so that we
know exactly how they're 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.
=head2 Conventions
In the following tables:
=over 3
=item C<t>
is a type.
=item C<p>
is a pointer.
=item C<n>
is a number.
=item C<s>
is a string.
=back
C<sv>, C<av>, C<hv>, etc. represent variables of their respective types.
=head2 File Operations
Instead of the F<stdio.h> functions, you should use the Perl abstraction
layer. Instead of C<FILE*> types, you need to be handling C<PerlIO*>
types. Don't forget that with the new PerlIO layered I/O abstraction
C<FILE*> types may not even be available. See also the C<perlapio>
documentation 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)
=head2 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 C<fread> and C<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 C<fgets>; one should use C<sv_gets> instead:
fgets(s, n, stream) sv_gets(sv, perlio, append)
=head2 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)
=head2 Memory Management and String Handling
Instead Of: Use:
t* p = malloc(n) New(id, p, n, t)
t* p = calloc(n, s) Newz(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 doesn't 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 C<Copy> and C<Move> than used
in C<memcpy> and C<memmove>.
Most of the time, though, you'll want to be dealing with SVs internally
instead of raw C<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 C<sv_catpvf> and C<sv_vcatpvfn>, combining
concatenation with formatting.
=head2 Character Class Tests
There are two types of character class tests that Perl implements: one
type deals in C<char>s and are thus B<not> Unicode aware (and hence
deprecated unless you B<know> you should use them) and the other type
deal in C<UV>s and know about Unicode properties. In the following
table, C<c> is a C<char>, and C<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)
=head2 F<stdlib.h> functions
Instead Of: Use:
atof(s) Atof(s)
atol(s) Atol(s)
strtod(s, *p) Nothing. Just don't use it.
strtol(s, *p, n) Strtol(s, *p, n)
strtoul(s, *p, n) Strtoul(s, *p, n)
Notice also the C<grok_bin>, C<grok_hex>, and C<grok_oct> functions in
F<numeric.c> for converting strings representing numbers in the respective
bases into C<NV>s.
In theory C<Strtol> and C<Strtoul> may not be defined if the machine perl is
built on doesn't actually have strtol and strtoul. But as those 2
functions are part of the 1989 ANSI C spec we suspect you'll 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) Don't. Look at pp_system or use my_popen
getenv(s) PerlEnv_getenv(s)
setenv(s, val) my_putenv(s, val)
=head2 Miscellaneous functions
You should not even B<want> to use F<setjmp.h> functions, but if you
think you do, use the C<JMPENV> stack in F<scope.h> instead.
For C<signal>/C<sigaction>, use C<rsignal(signo, handler)>.
=head1 SEE ALSO
C<perlapi>, C<perlapio>, C<perlguts>