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perlclib (1)


perlclib - Internal replacements for standard C library functions


Please see following description for synopsis


Perl Programmers Reference Guide                      PERLCLIB(1)

     perlclib - Internal replacements for standard C library

     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.

     In the following tables:

        is a type.

        is a pointer.

        is a number.

        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)

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         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"

         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(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!)

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         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()
     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 "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)

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Perl Programmers Reference Guide                      PERLCLIB(1)

         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 attributes(5) for descriptions of the following

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Perl Programmers Reference Guide                      PERLCLIB(1)

     |Availability   | runtime/perl-512 |
     |Stability      | Uncommitted      |
     perlapi, perlapio, perlguts

     This software was built from source available at  The original
     community source was downloaded from

     Further information about this software can be found on the
     open source community website at

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