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/*(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.
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 v5.8.8 2006-01-07 PERLCLIB(1)
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