1PERLCLIB(1) Perl Programmers Reference Guide PERLCLIB(1)
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6 perlclib - Internal replacements for standard C library functions
7
9 One thing Perl porters should note is that perl doesn't tend to use
10 that much of the C standard library internally; you'll see very little
11 use of, for example, the ctype.h functions in there. This is because
12 Perl tends to reimplement or abstract standard library functions, so
13 that we know exactly how they're going to operate.
14 This is a reference card for people who are familiar with the C library
16 and who want to do things the Perl way; to tell them which functions
17 they ought to use instead of the more normal C functions.
18 Conventions
20 In the following tables:
21 "t"
23 is a type.
24 "p"
26 is a pointer.
27 "n"
29 is a number.
30 "s"
32 is a string.
33 "sv", "av", "hv", etc. represent variables of their respective types.
35 File Operations
37 Instead of the stdio.h functions, you should use the Perl abstraction
38 layer. Instead of "FILE*" types, you need to be handling "PerlIO*"
39 types. Don't forget that with the new PerlIO layered I/O abstraction
40 "FILE*" types may not even be available. See also the "perlapio"
41 documentation for more information about the following functions:
42 Instead Of: Use:
44 stdin PerlIO_stdin()
46 stdout PerlIO_stdout()
47 stderr PerlIO_stderr()
48 fopen(fn, mode) PerlIO_open(fn, mode)
50 freopen(fn, mode, stream) PerlIO_reopen(fn, mode, perlio) (Dep-
51 recated)
52 fflush(stream) PerlIO_flush(perlio)
53 fclose(stream) PerlIO_close(perlio)
54 File Input and Output
56 Instead Of: Use:
57 fprintf(stream, fmt, ...) PerlIO_printf(perlio, fmt, ...)
59 [f]getc(stream) PerlIO_getc(perlio)
61 [f]putc(stream, n) PerlIO_putc(perlio, n)
62 ungetc(n, stream) PerlIO_ungetc(perlio, n)
63 Note that the PerlIO equivalents of "fread" and "fwrite" are slightly
65 different from their C library counterparts:
66 fread(p, size, n, stream) PerlIO_read(perlio, buf, numbytes)
68 fwrite(p, size, n, stream) PerlIO_write(perlio, buf, numbytes)
69 fputs(s, stream) PerlIO_puts(perlio, s)
71 There is no equivalent to "fgets"; one should use "sv_gets" instead:
73 fgets(s, n, stream) sv_gets(sv, perlio, append)
75 File Positioning
77 Instead Of: Use:
78 feof(stream) PerlIO_eof(perlio)
80 fseek(stream, n, whence) PerlIO_seek(perlio, n, whence)
81 rewind(stream) PerlIO_rewind(perlio)
82 fgetpos(stream, p) PerlIO_getpos(perlio, sv)
84 fsetpos(stream, p) PerlIO_setpos(perlio, sv)
85 ferror(stream) PerlIO_error(perlio)
87 clearerr(stream) PerlIO_clearerr(perlio)
88 Memory Management and String Handling
90 Instead Of: Use:
91 t* p = malloc(n) Newx(p, n, t)
93 t* p = calloc(n, s) Newxz(p, n, t)
94 p = realloc(p, n) Renew(p, n, t)
95 memcpy(dst, src, n) Copy(src, dst, n, t)
96 memmove(dst, src, n) Move(src, dst, n, t)
97 memcpy(dst, src, sizeof(t)) StructCopy(src, dst, t)
98 memset(dst, 0, n * sizeof(t)) Zero(dst, n, t)
99 memzero(dst, 0) Zero(dst, n, char)
100 free(p) Safefree(p)
101 strdup(p) savepv(p)
103 strndup(p, n) savepvn(p, n) (Hey, strndup doesn't
104 exist!)
105 strstr(big, little) instr(big, little)
107 strcmp(s1, s2) strLE(s1, s2) / strEQ(s1, s2)
108 / strGT(s1,s2)
109 strncmp(s1, s2, n) strnNE(s1, s2, n) / strnEQ(s1, s2, n)
110 memcmp(p1, p2, n) memNE(p1, p2, n)
112 !memcmp(p1, p2, n) memEQ(p1, p2, n)
113 Notice the different order of arguments to "Copy" and "Move" than used
115 in "memcpy" and "memmove".
116 Most of the time, though, you'll want to be dealing with SVs internally
118 instead of raw "char *" strings:
119 strlen(s) sv_len(sv)
121 strcpy(dt, src) sv_setpv(sv, s)
122 strncpy(dt, src, n) sv_setpvn(sv, s, n)
123 strcat(dt, src) sv_catpv(sv, s)
124 strncat(dt, src) sv_catpvn(sv, s)
125 sprintf(s, fmt, ...) sv_setpvf(sv, fmt, ...)
126 Note also the existence of "sv_catpvf" and "sv_vcatpvfn", combining
128 concatenation with formatting.
129 Sometimes instead of zeroing the allocated heap by using Newxz() you
131 should consider "poisoning" the data. This means writing a bit pattern
132 into it that should be illegal as pointers (and floating point
133 numbers), and also hopefully surprising enough as integers, so that any
134 code attempting to use the data without forethought will break sooner
135 rather than later. Poisoning can be done using the Poison() macros,
136 which have similar arguments to Zero():
137 PoisonWith(dst, n, t, b) scribble memory with byte b
139 PoisonNew(dst, n, t) equal to PoisonWith(dst, n, t, 0xAB)
140 PoisonFree(dst, n, t) equal to PoisonWith(dst, n, t, 0xEF)
141 Poison(dst, n, t) equal to PoisonFree(dst, n, t)
142 Character Class Tests
144 There are several types of character class tests that Perl implements.
145 The only ones described here are those that directly correspond to C
146 library functions that operate on 8-bit characters, but there are
147 equivalents that operate on wide characters, and UTF-8 encoded strings.
148 All are more fully described in "Character classification" in perlapi
149 and "Character case changing" in perlapi.
150 The C library routines listed in the table below return values based on
152 the current locale. Use the entries in the final column for that
153 functionality. The other two columns always assume a POSIX (or C)
154 locale. The entries in the ASCII column are only meaningful for ASCII
155 inputs, returning FALSE for anything else. Use these only when you
156 know that is what you want. The entries in the Latin1 column assume
157 that the non-ASCII 8-bit characters are as Unicode defines, them, the
158 same as ISO-8859-1, often called Latin 1.
159 Instead Of: Use for ASCII: Use for Latin1: Use for locale:
161 isalnum(c) isALPHANUMERIC(c) isALPHANUMERIC_L1(c) isALPHANUMERIC_LC(c)
163 isalpha(c) isALPHA(c) isALPHA_L1(c) isALPHA_LC(u )
164 isascii(c) isASCII(c) isASCII_LC(c)
165 isblank(c) isBLANK(c) isBLANK_L1(c) isBLANK_LC(c)
166 iscntrl(c) isCNTRL(c) isCNTRL_L1(c) isCNTRL_LC(c)
167 isdigit(c) isDIGIT(c) isDIGIT_L1(c) isDIGIT_LC(c)
168 isgraph(c) isGRAPH(c) isGRAPH_L1(c) isGRAPH_LC(c)
169 islower(c) isLOWER(c) isLOWER_L1(c) isLOWER_LC(c)
170 isprint(c) isPRINT(c) isPRINT_L1(c) isPRINT_LC(c)
171 ispunct(c) isPUNCT(c) isPUNCT_L1(c) isPUNCT_LC(c)
172 isspace(c) isSPACE(c) isSPACE_L1(c) isSPACE_LC(c)
173 isupper(c) isUPPER(c) isUPPER_L1(c) isUPPER_LC(c)
174 isxdigit(c) isXDIGIT(c) isXDIGIT_L1(c) isXDIGIT_LC(c)
175 tolower(c) toLOWER(c) toLOWER_L1(c)
177 toupper(c) toUPPER(c)
178 To emphasize that you are operating only on ASCII characters, you can
180 append "_A" to each of the macros in the ASCII column: "isALPHA_A",
181 "isDIGIT_A", and so on.
182 (There is no entry in the Latin1 column for "isascii" even though there
184 is an "isASCII_L1", which is identical to "isASCII"; the latter name
185 is clearer. There is no entry in the Latin1 column for "toupper"
186 because the result can be non-Latin1. You have to use "toUPPER_uvchr",
187 as described in "Character case changing" in perlapi.)
188 stdlib.h functions
190 Instead Of: Use:
191 atof(s) Atof(s)
193 atoi(s) grok_atoUV(s, &uv, &e)
194 atol(s) grok_atoUV(s, &uv, &e)
195 strtod(s, &p) Strtod(s, &p)
196 strtol(s, &p, n) Strtol(s, &p, b)
197 strtoul(s, &p, n) Strtoul(s, &p, b)
198 Typical use is to do range checks on "uv" before casting:
200 int i; UV uv;
202 char* end_ptr = input_end;
203 if (grok_atoUV(input, &uv, &end_ptr)
204 && uv <= INT_MAX)
205 i = (int)uv;
206 ... /* continue parsing from end_ptr */
207 } else {
208 ... /* parse error: not a decimal integer in range 0 .. MAX_IV */
209 }
210 Notice also the "grok_bin", "grok_hex", and "grok_oct" functions in
212 numeric.c for converting strings representing numbers in the respective
213 bases into "NV"s. Note that grok_atoUV() doesn't handle negative
214 inputs, or leading whitespace (being purposefully strict).
215 Note that strtol() and strtoul() may be disguised as Strtol(),
217 Strtoul(), Atol(), Atoul(). Avoid those, too.
218 In theory "Strtol" and "Strtoul" may not be defined if the machine perl
220 is built on doesn't actually have strtol and strtoul. But as those 2
221 functions are part of the 1989 ANSI C spec we suspect you'll find them
222 everywhere by now.
223 int rand() double Drand01()
225 srand(n) { seedDrand01((Rand_seed_t)n);
226 PL_srand_called = TRUE; }
227 exit(n) my_exit(n)
229 system(s) Don't. Look at pp_system or use my_popen.
230 getenv(s) PerlEnv_getenv(s)
232 setenv(s, val) my_setenv(s, val)
233 Miscellaneous functions
235 You should not even want to use setjmp.h functions, but if you think
236 you do, use the "JMPENV" stack in scope.h instead.
237 For "signal"/"sigaction", use "rsignal(signo, handler)".
239
241 perlapi, perlapio, perlguts
242perl v5.36.0 2022-08-30 PERLCLIB(1)