perlclib - Internal replacements for standard C library functions
One thing Perl porters should note is thatperl doesn't tend to use that much of the C standard library internally; you'll see very little use of, for example, thectype.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.
In the following tables:
sv,av,hv, etc. represent variables of their respective types.
Instead of thestdio.h functions, you should use the Perl abstraction layer. Instead ofFILE* types, you need to be handlingPerlIO* types. Don't forget that with the new PerlIO layered I/O abstractionFILE* types may not even be available. See also theperlapio 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)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 offread andfwrite 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 tofgets; one should usesv_gets instead:
fgets(s, n, stream) sv_gets(sv, perlio, append)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)Instead Of: Use:t* p = malloc(n) New(id, p, n, t)t* p = calloc(n, s) Newz(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 toCopy andMove than used inmemcpy andmemmove.
Most of the time, though, you'll want to be dealing with SVs internally instead of rawchar * 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 ofsv_catpvf andsv_vcatpvfn, combining concatenation with formatting.
Sometimes instead of zeroing the allocated heap by using Newz() 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)There are two types of character class tests that Perl implements: one type deals inchars and are thusnot Unicode aware (and hence deprecated unless youknow you should use them) and the other type deal inUVs and know about Unicode properties. In the following table,c is achar, andu 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)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 thegrok_bin,grok_hex, andgrok_oct functions innumeric.c for converting strings representing numbers in the respective bases intoNVs.
In theoryStrtol andStrtoul 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_popengetenv(s) PerlEnv_getenv(s)setenv(s, val) my_putenv(s, val)You should not evenwant to usesetjmp.h functions, but if you think you do, use theJMPENV stack inscope.h instead.
Forsignal/sigaction, usersignal(signo, handler).
perlapi,perlapio,perlguts
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