1/* 2 * Style guide for the 4BSD KNF (Kernel Normal Form). 3 * 4 * @(#)style 1.14 (Berkeley) 04/28/95 5 */ 6 7/* 8 * VERY important single-line comments look like this. 9 */ 10 11/* Most single-line comments look like this. */ 12 13/* 14 * Multi-line comments look like this. Make them real sentences. Fill 15 * them so they look like real paragraphs. 16 */ 17 18/* 19 * Kernel include files come first; normally, you'll need <sys/types.h> 20 * OR <sys/param.h>, but not both! <sys/types.h> includes <sys/cdefs.h>, 21 * and it's okay to depend on that. 22 */ 23#include <sys/types.h> /* Non-local includes in brackets. */ 24 25/* If it's a network program, put the network include files next. */ 26#include <net/if.h> 27#include <net/if_dl.h> 28#include <net/route.h> 29#include <netinet/in.h> 30#include <protocols/rwhod.h> 31 32/* 33 * Then there's a blank line, followed by the /usr include files. 34 * The /usr include files should be sorted! 35 */ 36#include <stdio.h> 37 38/* 39 * Global pathnames are defined in /usr/include/paths.h. Pathnames local 40 * to the program go in pathnames.h in the local directory. 41 */ 42#include <paths.h> 43 44/* Then, there's a blank line, and the user include files. */ 45#include "pathnames.h" /* Local includes in double quotes. */ 46 47/* 48 * Macros are capitalized, parenthesized, and should avoid side-effects. 49 * If they are an inline expansion of a function, the function is defined 50 * all in lowercase, the macro has the same name all in uppercase. If the 51 * macro needs more than a single line, use braces. Right-justify the 52 * backslashes, it makes it easier to read. 53 */ 54#define MACRO(x, y) { \ 55 variable = (x) + (y); \ 56 (y) += 2; \ 57} 58 59/* Enum types are capitalized. */ 60enum enumtype { ONE, TWO } et; 61 62/* 63 * When declaring variables in structures, declare them sorted by use, then 64 * by size, and then by alphabetical order. The first category normally 65 * doesn't apply, but there are exceptions. Each one gets its own line. 66 * Put a tab after the first word, i.e. use "int^Ix;" and "struct^Ifoo *x;". 67 * 68 * Major structures should be declared at the top of the file in which they 69 * are used, or in separate header files, if they are used in multiple 70 * source files. Use of the structures should be by separate declarations 71 * and should be "extern" if they are declared in a header file. 72 */ 73struct foo { 74 struct foo *next; /* List of active foo */ 75 struct mumble amumble; /* Comment for mumble */ 76 int bar; 77}; 78struct foo *foohead; /* Head of global foo list */ 79 80/* Make the structure name match the typedef. */ 81typedef struct _bar { 82 int level; 83} BAR; 84 85/* 86 * ANSI function declarations for private functions (i.e. functions not used 87 * elsewhere) go at the top of the first source module. Use the __P macro 88 * from the include file <sys/cdefs.h>. Only the kernel has a name associated 89 * with the types, i.e. in the kernel use: 90 * 91 * void function __P((int fd)); 92 * 93 * in user land use: 94 * 95 * void function __P((int)); 96 */ 97static char *function __P((int, const char *)); 98static void usage __P((void)); 99 100/* 101 * All major routines should have a comment briefly describing what 102 * they do. The comment before the "main" routine should describe 103 * what the program does. 104 */ 105int 106main(argc, argv) 107 int argc; 108 char *argv[]; 109{ 110 extern char *optarg; 111 extern int optind; 112 long num; 113 int ch; 114 char *ep; 115 116 /* 117 * For consistency, getopt should be used to parse options. Options 118 * should be sorted in the getopt call and the switch statement, unless 119 * parts of the switch cascade. Elements in a switch statement that 120 * cascade should have a FALLTHROUGH comment. Numerical arguments 121 * should be checked for accuracy. Code that cannot be reached should 122 * have a NOTREACHED comment. 123 */ 124 while ((ch = getopt(argc, argv, "abn")) != EOF) 125 switch (ch) { /* Indent the switch. */ 126 case 'a': /* Don't indent the case. */ 127 aflag = 1; 128 /* FALLTHROUGH */ 129 case 'b': 130 bflag = 1; 131 break; 132 case 'n': 133 num = strtol(optarg, &ep, 10); 134 if (num <= 0 || *ep != '\0') 135 err("illegal number -- %s", optarg); 136 break; 137 case '?': 138 default: 139 usage(); 140 /* NOTREACHED */ 141 } 142 argc -= optind; 143 argv += optind; 144 145 /* 146 * Space after keywords (while, for, return, switch). No braces are 147 * used for control statements with zero or only a single statement. 148 * 149 * Forever loops are done with for's, not while's. 150 */ 151 for (p = buf; *p != '\0'; ++p); 152 for (;;) 153 stmt; 154 155 /* 156 * Parts of a for loop may be left empty. Don't put declarations 157 * inside blocks unless the routine is unusually complicated. 158 */ 159 for (; cnt < 15; cnt++) { 160 stmt1; 161 stmt2; 162 } 163 164 /* Second level indents are four spaces. */ 165 while (cnt < 20) 166 z = a + really + long + statment + that + needs + two lines + 167 gets + indented + four + spaces + on + the + second + 168 and + subsequent + lines. 169 170 /* 171 * Closing and opening braces go on the same line as the else. 172 * Don't add braces that aren't necessary. 173 */ 174 if (test) 175 stmt; 176 else if (bar) { 177 stmt; 178 stmt; 179 } else 180 stmt; 181 182 /* No spaces after function names. */ 183 if (error = function(a1, a2)) 184 exit(error); 185 186 /* 187 * Unary operators don't require spaces, binary operators do. Don't 188 * use parenthesis unless they're required for precedence, or the 189 * statement is really confusing without them. 190 */ 191 a = b->c[0] + ~d == (e || f) || g && h ? i : j >> 1; 192 k = !(l & FLAGS); 193 194 /* 195 * Exits should be 0 on success, and 1 on failure. Don't denote 196 * all the possible exit points, using the integers 1 through 300. 197 */ 198 exit(0); /* Avoid obvious comments such as "Exit 0 on success." */ 199} 200 201/* 202 * If a function type is declared, it should be on a line 203 * by itself preceeding the function. 204 */ 205static char * 206function(a1, a2, fl, a4) 207 int a1, a2, a4; /* Declare ints, too, don't default them. */ 208 float fl; /* List in order declared, as much as possible. */ 209{ 210 /* 211 * When declaring variables in functions declare them sorted by size, 212 * then in alphabetical order; multiple ones per line are okay. Old 213 * style function declarations can go on the same line. ANSI style 214 * function declarations should go in the include file "extern.h". 215 * If a line overflows reuse the type keyword. 216 * 217 * DO NOT initialize variables in the declarations. 218 */ 219 extern u_char one; 220 extern char two; 221 struct foo three, *four; 222 double five; 223 int *six, seven, eight(); 224 char *nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen; 225 char *overflow __P((void)); 226 void *mymalloc __P((u_int)); 227 228 /* 229 * Casts and sizeof's are not followed by a space. NULL is any 230 * pointer type, and doesn't need to be cast, so use NULL instead 231 * of (struct foo *)0 or (struct foo *)NULL. Also, test pointers 232 * against NULL, i.e. use: 233 * 234 * (p = f()) == NULL 235 * not: 236 * !(p = f()) 237 * 238 * Don't use '!' for tests unless it's a boolean, e.g. use 239 * "if (*p == '\0')", not "if (!*p)". 240 * 241 * Routines returning void * should not have their return values cast 242 * to any pointer type. 243 * 244 * Use err/warn(3), don't roll your own! 245 */ 246 if ((four = malloc(sizeof(struct foo))) == NULL) 247 err(1, NULL); 248 if ((six = (int *)overflow()) == NULL) 249 errx(1, "Number overflowed."); 250 return (eight); 251} 252 253/* 254 * Don't use ANSI function declarations unless you absolutely have too, 255 * i.e. you're declaring functions with variable numbers of arguments. 256 * 257 * ANSI function return values and braces look like regular functions. 258 */ 259int 260function(int a1, int a2) 261{ 262 ... 263} 264 265/* Variable numbers of arguments should look like this. */ 266#if __STDC__ 267#include <stdarg.h> 268#else 269#include <varargs.h> 270#endif 271 272void 273#if __STDC__ 274vaf(const char *fmt, ...) 275#else 276vaf(fmt, va_alist) 277 char *fmt; 278 va_dcl 279#endif 280{ 281 va_list ap; 282#if __STDC__ 283 va_start(ap, fmt); 284#else 285 va_start(ap); 286#endif 287 STUFF; 288 289 va_end(ap); /* No return needed for void functions. */ 290} 291 292static void 293usage() 294{ /* Insert an empty line if the function has no local variables. */ 295 296 /* 297 * Use printf(3), not fputs/puts/putchar/whatever, it's faster and 298 * usually cleaner, not to mention avoiding stupid bugs. 299 * 300 * Usage statements should look like the manual pages. Options w/o 301 * operands come first, in alphabetical order inside a single set of 302 * braces. Followed by options with operands, in alphabetical order, 303 * each in braces. Followed by required arguments in the order they 304 * are specified, followed by optional arguments in the order they 305 * are specified. A bar ('|') separates either/or options/arguments, 306 * and multiple options/arguments which are specified together are 307 * placed in a single set of braces. 308 * 309 * "usage: f [-ade] [-b b_arg] [-m m_arg] req1 req2 [opt1 [opt2]]\n" 310 * "usage: f [-a | -b] [-c [-de] [-n number]]\n" 311 */ 312 (void)fprintf(stderr, "usage: f [-ab]\n"); 313 exit(1); 314} 315