PERLCLIB(1) Perl Programmers Reference Guide PERLCLIB(1)
perlclib - Internal replacements for standard C library
functions
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 reimple-
ment 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 respec-
tive 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()
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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:
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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 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() 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 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.
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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" func-
tions 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.
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For "signal"/"sigaction", use "rsignal(signo, handler)".
"perlapi", "perlapio", "perlguts"
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