perlclib
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) (Dep-
recated)
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(p, n, t)
t* p = calloc(n, s) Newxz(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)
memcmp(p1, p2, n) memNE(p1, p2, n)
!memcmp(p1, p2, n) memEQ(p1, p2, 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 several types of character class tests that Perl implements.
The only ones described here are those that directly correspond to C
library functions that operate on 8-bit characters, but there are
equivalents that operate on wide characters, and UTF-8 encoded strings.
All are more fully described in "Character classification" in perlapi
and "Character case changing" in perlapi.
The C library routines listed in the table below return values based on
the current locale. Use the entries in the final column for that
functionality. The other two columns always assume a POSIX (or C)
locale. The entries in the ASCII column are only meaningful for ASCII
inputs, returning FALSE for anything else. Use these only when you
know that is what you want. The entries in the Latin1 column assume
that the non-ASCII 8-bit characters are as Unicode defines, them, the
same as ISO-8859-1, often called Latin 1.
Instead Of: Use for ASCII: Use for Latin1: Use for locale:
isalnum(c) isALPHANUMERIC(c) isALPHANUMERIC_L1(c) isALPHANUMERIC_LC(c)
isalpha(c) isALPHA(c) isALPHA_L1(c) isALPHA_LC(u )
isascii(c) isASCII(c) isASCII_LC(c)
isblank(c) isBLANK(c) isBLANK_L1(c) isBLANK_LC(c)
iscntrl(c) isCNTRL(c) isCNTRL_L1(c) isCNTRL_LC(c)
isdigit(c) isDIGIT(c) isDIGIT_L1(c) isDIGIT_LC(c)
isgraph(c) isGRAPH(c) isGRAPH_L1(c) isGRAPH_LC(c)
islower(c) isLOWER(c) isLOWER_L1(c) isLOWER_LC(c)
isprint(c) isPRINT(c) isPRINT_L1(c) isPRINT_LC(c)
ispunct(c) isPUNCT(c) isPUNCT_L1(c) isPUNCT_LC(c)
isspace(c) isSPACE(c) isSPACE_L1(c) isSPACE_LC(c)
isupper(c) isUPPER(c) isUPPER_L1(c) isUPPER_LC(c)
isxdigit(c) isXDIGIT(c) isXDIGIT_L1(c) isXDIGIT_LC(c)
tolower(c) toLOWER(c) toLOWER_L1(c) toLOWER_LC(c)
toupper(c) toUPPER(c) toUPPER_LC(c)
To emphasize that you are operating only on ASCII characters, you can
append "_A" to each of the macros in the ASCII column: "isALPHA_A",
"isDIGIT_A", and so on.
(There is no entry in the Latin1 column for "isascii" even though there
is an "isASCII_L1", which is identical to "isASCII"; the latter name
is clearer. There is no entry in the Latin1 column for "toupper"
because the result can be non-Latin1. You have to use "toUPPER_uni",
as described in "Character case changing" in perlapi.)
stdlib.h functions
Instead Of: Use:
atof(s) Atof(s)
atoi(s) grok_atoUV(s, &uv, &e)
atol(s) grok_atoUV(s, &uv, &e)
strtod(s, &p) my_atof3(s, &nv, &p) is the closest we have
strtol(s, &p, n) grok_atoUV(s, &uv, &e)
strtoul(s, &p, n) grok_atoUV(s, &uv, &e)
Typical use is to do range checks on "uv" before casting:
int i; UV uv;
char* end_ptr = input_end;
if (grok_atoUV(input, &uv, &end_ptr)
&& uv <= INT_MAX)
i = (int)uv;
... /* continue parsing from end_ptr */
} else {
... /* parse error: not a decimal integer in range 0 .. MAX_IV */
}
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. Note that grok_atoUV() doesn't handle negative
inputs, or leading whitespace (being purposefully strict).
Note that strtol() and strtoul() may be disguised as Strtol(),
Strtoul(), Atol(), Atoul(). Avoid those, too.
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_setenv(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 v5.30.0 2023-11-23 PERLCLIB(1)
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