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
perlapiodocumentation 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
freadand
fwriteare 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_getsinstead:
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
Copyand
Movethan used in
memcpyand
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_catpvfand
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 as 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
chars and are thus not Unicode aware (and hence deprecated unless you know you should use them) and the other type deal in
UVs and know about Unicode properties. In the following table,
cis a
char, and
uis 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)
\fIstdlib.h\fP 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_octfunctions in numeric.c for converting strings representing numbers in the respective bases into
NVs.
In theory
Strtoland
Strtoulmay 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
JMPENVstack in scope.h instead.
For
signal/
sigaction, use
rsignal(signo, handler).
SEE ALSO
perlapi,
perlapio,
perlguts