Next: perlcompile | Previous: perlcc |  | [Table of Contents] | [Index]

# perlclib

- NAME
- DESCRIPTION
  - Conventions
  - File Operations
  - File Input and Output
  - File Positioning
  - Memory Management and String Handling
  - Character Class Tests
  - `stdlib.h` functions
  - Miscellaneous functions
- SEE ALSO

## 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)            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)
        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_catpvfn`, combining concatenation with formatting.

### 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, 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 `scan_bin`, `scan_hex`, and `scan_oct` functions in `util.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`

[Top] Generated by Pod::HTML 0.43 on Mon Mar 19 17:34:55 2001