3 perlclib - Internal replacements for standard C library functions
7 One thing Perl porters should note is that F<perl> doesn't tend to use that
8 much of the C standard library internally; you'll see very little use of,
9 for example, the F<ctype.h> functions in there. This is because Perl
10 tends to reimplement or abstract standard library functions, so that we
11 know exactly how they're going to operate.
13 This is a reference card for people who are familiar with the C library
14 and who want to do things the Perl way; to tell them which functions
15 they ought to use instead of the more normal C functions.
19 In the following tables:
41 C<sv>, C<av>, C<hv>, etc. represent variables of their respective types.
43 =head2 File Operations
45 Instead of the F<stdio.h> functions, you should use the Perl abstraction
46 layer. Instead of C<FILE*> types, you need to be handling C<PerlIO*>
47 types. Don't forget that with the new PerlIO layered I/O abstraction
48 C<FILE*> types may not even be available. See also the C<perlapio>
49 documentation for more information about the following functions:
54 stdout PerlIO_stdout()
55 stderr PerlIO_stderr()
57 fopen(fn, mode) PerlIO_open(fn, mode)
58 freopen(fn, mode, stream) PerlIO_reopen(fn, mode, perlio) (Dep-
60 fflush(stream) PerlIO_flush(perlio)
61 fclose(stream) PerlIO_close(perlio)
63 =head2 File Input and Output
67 fprintf(stream, fmt, ...) PerlIO_printf(perlio, fmt, ...)
69 [f]getc(stream) PerlIO_getc(perlio)
70 [f]putc(stream, n) PerlIO_putc(perlio, n)
71 ungetc(n, stream) PerlIO_ungetc(perlio, n)
73 Note that the PerlIO equivalents of C<fread> and C<fwrite> are slightly
74 different from their C library counterparts:
76 fread(p, size, n, stream) PerlIO_read(perlio, buf, numbytes)
77 fwrite(p, size, n, stream) PerlIO_write(perlio, buf, numbytes)
79 fputs(s, stream) PerlIO_puts(perlio, s)
81 There is no equivalent to C<fgets>; one should use C<sv_gets> instead:
83 fgets(s, n, stream) sv_gets(sv, perlio, append)
85 =head2 File Positioning
89 feof(stream) PerlIO_eof(perlio)
90 fseek(stream, n, whence) PerlIO_seek(perlio, n, whence)
91 rewind(stream) PerlIO_rewind(perlio)
93 fgetpos(stream, p) PerlIO_getpos(perlio, sv)
94 fsetpos(stream, p) PerlIO_setpos(perlio, sv)
96 ferror(stream) PerlIO_error(perlio)
97 clearerr(stream) PerlIO_clearerr(perlio)
99 =head2 Memory Management and String Handling
103 t* p = malloc(n) Newx(p, n, t)
104 t* p = calloc(n, s) Newxz(p, n, t)
105 p = realloc(p, n) Renew(p, n, t)
106 memcpy(dst, src, n) Copy(src, dst, n, t)
107 memmove(dst, src, n) Move(src, dst, n, t)
108 memcpy(dst, src, sizeof(t)) StructCopy(src, dst, t)
109 memset(dst, 0, n * sizeof(t)) Zero(dst, n, t)
110 memzero(dst, 0) Zero(dst, n, char)
114 strndup(p, n) savepvn(p, n) (Hey, strndup doesn't
117 strstr(big, little) instr(big, little)
118 strcmp(s1, s2) strLE(s1, s2) / strEQ(s1, s2)
120 strncmp(s1, s2, n) strnNE(s1, s2, n) / strnEQ(s1, s2, n)
122 memcmp(p1, p2, n) memNE(p1, p2, n)
123 !memcmp(p1, p2, n) memEQ(p1, p2, n)
125 Notice the different order of arguments to C<Copy> and C<Move> than used
126 in C<memcpy> and C<memmove>.
128 Most of the time, though, you'll want to be dealing with SVs internally
129 instead of raw C<char *> strings:
132 strcpy(dt, src) sv_setpv(sv, s)
133 strncpy(dt, src, n) sv_setpvn(sv, s, n)
134 strcat(dt, src) sv_catpv(sv, s)
135 strncat(dt, src) sv_catpvn(sv, s)
136 sprintf(s, fmt, ...) sv_setpvf(sv, fmt, ...)
138 Note also the existence of C<sv_catpvf> and C<sv_vcatpvfn>, combining
139 concatenation with formatting.
141 Sometimes instead of zeroing the allocated heap by using Newxz() you
142 should consider "poisoning" the data. This means writing a bit
143 pattern into it that should be illegal as pointers (and floating point
144 numbers), and also hopefully surprising enough as integers, so that
145 any code attempting to use the data without forethought will break
146 sooner rather than later. Poisoning can be done using the Poison()
147 macros, which have similar arguments to Zero():
149 PoisonWith(dst, n, t, b) scribble memory with byte b
150 PoisonNew(dst, n, t) equal to PoisonWith(dst, n, t, 0xAB)
151 PoisonFree(dst, n, t) equal to PoisonWith(dst, n, t, 0xEF)
152 Poison(dst, n, t) equal to PoisonFree(dst, n, t)
154 =head2 Character Class Tests
156 There are several types of character class tests that Perl implements.
157 The only ones described here are those that directly correspond to C
158 library functions that operate on 8-bit characters, but there are
159 equivalents that operate on wide characters, and UTF-8 encoded strings.
160 All are more fully described in L<perlapi/Character classification> and
161 L<perlapi/Character case changing>.
163 The C library routines listed in the table below return values based on
164 the current locale. Use the entries in the final column for that
165 functionality. The other two columns always assume a POSIX (or C)
166 locale. The entries in the ASCII column are only meaningful for ASCII
167 inputs, returning FALSE for anything else. Use these only when you
168 B<know> that is what you want. The entries in the Latin1 column assume
169 that the non-ASCII 8-bit characters are as Unicode defines, them, the
170 same as ISO-8859-1, often called Latin 1.
172 Instead Of: Use for ASCII: Use for Latin1: Use for locale:
174 isalnum(c) isALPHANUMERIC(c) isALPHANUMERIC_L1(c) isALPHANUMERIC_LC(c)
175 isalpha(c) isALPHA(c) isALPHA_L1(c) isALPHA_LC(u )
176 isascii(c) isASCII(c) isASCII_LC(c)
177 isblank(c) isBLANK(c) isBLANK_L1(c) isBLANK_LC(c)
178 iscntrl(c) isCNTRL(c) isCNTRL_L1(c) isCNTRL_LC(c)
179 isdigit(c) isDIGIT(c) isDIGIT_L1(c) isDIGIT_LC(c)
180 isgraph(c) isGRAPH(c) isGRAPH_L1(c) isGRAPH_LC(c)
181 islower(c) isLOWER(c) isLOWER_L1(c) isLOWER_LC(c)
182 isprint(c) isPRINT(c) isPRINT_L1(c) isPRINT_LC(c)
183 ispunct(c) isPUNCT(c) isPUNCT_L1(c) isPUNCT_LC(c)
184 isspace(c) isSPACE(c) isSPACE_L1(c) isSPACE_LC(c)
185 isupper(c) isUPPER(c) isUPPER_L1(c) isUPPER_LC(c)
186 isxdigit(c) isXDIGIT(c) isXDIGIT_L1(c) isXDIGIT_LC(c)
188 tolower(c) toLOWER(c) toLOWER_L1(c) toLOWER_LC(c)
189 toupper(c) toUPPER(c) toUPPER_LC(c)
191 To emphasize that you are operating only on ASCII characters, you can
192 append C<_A> to each of the macros in the ASCII column: C<isALPHA_A>,
193 C<isDIGIT_A>, and so on.
195 (There is no entry in the Latin1 column for C<isascii> even though there
196 is an C<isASCII_L1>, which is identical to C<isASCII>; the
197 latter name is clearer. There is no entry in the Latin1 column for
198 C<toupper> because the result can be non-Latin1. You have to use
199 C<toUPPER_uni>, as described in L<perlapi/Character case changing>.)
201 =head2 F<stdlib.h> functions
206 atoi(s) grok_atou(s, &e)
207 atol(s) grok_atou(s, &e)
208 strtod(s, &p) Nothing. Just don't use it.
209 strtol(s, &p, n) grok_atou(s, &e)
210 strtoul(s, &p, n) grok_atou(s, &e)
212 Notice also the C<grok_bin>, C<grok_hex>, and C<grok_oct> functions in
213 F<numeric.c> for converting strings representing numbers in the respective
214 bases into C<NV>s. Note that grok_atou() doesn't handle negative inputs,
215 or leading whitespace (being purposefully strict).
217 Note that strtol() and strtoul() may be disguised as Strtol(), Strtoul(),
218 Atol(), Atoul(). Avoid those, too.
220 In theory C<Strtol> and C<Strtoul> may not be defined if the machine perl is
221 built on doesn't actually have strtol and strtoul. But as those 2
222 functions are part of the 1989 ANSI C spec we suspect you'll find them
225 int rand() double Drand01()
226 srand(n) { seedDrand01((Rand_seed_t)n);
227 PL_srand_called = TRUE; }
230 system(s) Don't. Look at pp_system or use my_popen.
232 getenv(s) PerlEnv_getenv(s)
233 setenv(s, val) my_setenv(s, val)
235 =head2 Miscellaneous functions
237 You should not even B<want> to use F<setjmp.h> functions, but if you
238 think you do, use the C<JMPENV> stack in F<scope.h> instead.
240 For C<signal>/C<sigaction>, use C<rsignal(signo, handler)>.
244 L<perlapi>, L<perlapio>, L<perlguts>