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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 doesn't tend to use that much of the C
standard library internally; you'll 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 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.
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. Don't forget that with the new
PerlIO layered I/O abstraction "FILE*" types may not even be available. See also the
"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)
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(dst, src, sizeof(t)) 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 "Copy" and "Move" than used in "memcpy" and
"memmove".
Most of the time, though, you'll 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 numbers), 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() macros, which have similar arguments
to Zero():
PoisonWith(dst, n, t, b) scribble memory with byte b
PoisonNew(dst, n, t) equal to PoisonWith(dst, n, t, 0xAB)
PoisonFree(dst, n, t) equal to PoisonWith(dst, n, t, 0xEF)
Poison(dst, n, t) equal to PoisonFree(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 deprecated 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 don't 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
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)
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 v5.16.3 2013-03-04 PERLCLIB(1)
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On Apache
Under GNU General Public License
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