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 Notice the different order of arguments to C<Copy> and C<Move> than used
123 in C<memcpy> and C<memmove>.
125 Most of the time, though, you'll want to be dealing with SVs internally
126 instead of raw C<char *> strings:
129 strcpy(dt, src) sv_setpv(sv, s)
130 strncpy(dt, src, n) sv_setpvn(sv, s, n)
131 strcat(dt, src) sv_catpv(sv, s)
132 strncat(dt, src) sv_catpvn(sv, s)
133 sprintf(s, fmt, ...) sv_setpvf(sv, fmt, ...)
135 Note also the existence of C<sv_catpvf> and C<sv_vcatpvfn>, combining
136 concatenation with formatting.
138 Sometimes instead of zeroing the allocated heap by using Newxz() you
139 should consider "poisoning" the data. This means writing a bit
140 pattern into it that should be illegal as pointers (and floating point
141 numbers), and also hopefully surprising enough as integers, so that
142 any code attempting to use the data without forethought will break
143 sooner rather than later. Poisoning can be done using the Poison()
144 macros, which have similar arguments to Zero():
146 PoisonWith(dst, n, t, b) scribble memory with byte b
147 PoisonNew(dst, n, t) equal to PoisonWith(dst, n, t, 0xAB)
148 PoisonFree(dst, n, t) equal to PoisonWith(dst, n, t, 0xEF)
149 Poison(dst, n, t) equal to PoisonFree(dst, n, t)
151 =head2 Character Class Tests
153 There are several types of character class tests that Perl implements.
154 The only ones described here are those that directly correspond to C
155 library functions that operate on 8-bit characters, but there are
156 equivalents that operate on wide characters, and UTF-8 encoded strings.
157 All are more fully described in L<perlapi/Character classification> and
158 L<perlapi/Character case changing>.
160 The C library routines listed in the table below return values based on
161 the current locale. Use the entries in the final column for that
162 functionality. The other two columns always assume a POSIX (or C)
163 locale. The entries in the ASCII column are only meaningful for ASCII
164 inputs, returning FALSE for anything else. Use these only when you
165 B<know> that is what you want. The entries in the Latin1 column assume
166 that the non-ASCII 8-bit characters are as Unicode defines, them, the
167 same as ISO-8859-1, often called Latin 1.
169 Instead Of: Use for ASCII: Use for Latin1: Use for locale:
171 isalnum(c) isALPHANUMERIC(c) isALPHANUMERIC_L1(c) isALPHANUMERIC_LC(c)
172 isalpha(c) isALPHA(c) isALPHA_L1(c) isALPHA_LC(u )
173 isascii(c) isASCII(c) isASCII_LC(c)
174 isblank(c) isBLANK(c) isBLANK_L1(c) isBLANK_LC(c)
175 iscntrl(c) isCNTRL(c) isCNTRL_L1(c) isCNTRL_LC(c)
176 isdigit(c) isDIGIT(c) isDIGIT_L1(c) isDIGIT_LC(c)
177 isgraph(c) isGRAPH(c) isGRAPH_L1(c) isGRAPH_LC(c)
178 islower(c) isLOWER(c) isLOWER_L1(c) isLOWER_LC(c)
179 isprint(c) isPRINT(c) isPRINT_L1(c) isPRINT_LC(c)
180 ispunct(c) isPUNCT(c) isPUNCT_L1(c) isPUNCT_LC(c)
181 isspace(c) isSPACE(c) isSPACE_L1(c) isSPACE_LC(c)
182 isupper(c) isUPPER(c) isUPPER_L1(c) isUPPER_LC(c)
183 isxdigit(c) isXDIGIT(c) isXDIGIT_L1(c) isXDIGIT_LC(c)
185 tolower(c) toLOWER(c) toLOWER_L1(c) toLOWER_LC(c)
186 toupper(c) toUPPER(c) toUPPER_LC(c)
188 To emphasize that you are operating only on ASCII characters, you can
189 append C<_A> to each of the macros in the ASCII column: C<isALPHA_A>,
190 C<isDIGIT_A>, and so on.
192 (There is no entry in the Latin1 column for C<isascii> even though there
193 is an C<isASCII_L1>, which is identical to C<isASCII>; the
194 latter name is clearer. There is no entry in the Latin1 column for
195 C<toupper> because the result can be non-Latin1. You have to use
196 C<toUPPER_uni>, as described in L<perlapi/Character case changing>.)
198 =head2 F<stdlib.h> functions
203 atoi(s) grok_atou(s, &e)
204 atol(s) grok_atou(s, &e)
205 strtod(s, &p) Nothing. Just don't use it.
206 strtol(s, &p, n) grok_atou(s, &e)
207 strtoul(s, &p, n) grok_atou(s, &e)
209 Notice also the C<grok_bin>, C<grok_hex>, and C<grok_oct> functions in
210 F<numeric.c> for converting strings representing numbers in the respective
211 bases into C<NV>s. Note that grok_atou() doesn't handle negative inputs,
212 or leading whitespace (being purposefully strict).
214 Note that strtol() and strtoul() may be disguised as Strtol(), Strtoul(),
215 Atol(), Atoul(). Avoid those, too.
217 In theory C<Strtol> and C<Strtoul> may not be defined if the machine perl is
218 built on doesn't actually have strtol and strtoul. But as those 2
219 functions are part of the 1989 ANSI C spec we suspect you'll find them
222 int rand() double Drand01()
223 srand(n) { seedDrand01((Rand_seed_t)n);
224 PL_srand_called = TRUE; }
227 system(s) Don't. Look at pp_system or use my_popen.
229 getenv(s) PerlEnv_getenv(s)
230 setenv(s, val) my_putenv(s, val)
232 =head2 Miscellaneous functions
234 You should not even B<want> to use F<setjmp.h> functions, but if you
235 think you do, use the C<JMPENV> stack in F<scope.h> instead.
237 For C<signal>/C<sigaction>, use C<rsignal(signo, handler)>.
241 L<perlapi>, L<perlapio>, L<perlguts>