📄 intro.2
字号:
4629(permits)S4959(the)S5110(sig-)S4680 V1330(naling)S1606(of)S1715(related)S2015(processes)S2426(\(see)S10 B(kill)140 2614 A10 R2754(\(2\)\).)S4848 V1080(Real)S1290(User)S1506(ID)S1638(and)S1808(Real)S(Group)257 2018 A2300(ID)S4968 V1330(Each)S1557(user)S1750(on)S1875(the)S2023(system)S2327(is)S2419(identi\256ed)S2824(by)S2949(a)S(positive)318 3019 A3362(integer)S3667(termed)S3972(the)S4120(real)S4297(user)S4490(ID.)S5136 V1330(Each)S1566(user)S1768(is)S1869(also)S2065(a)S2144(member)S2508(of)S2626(one)S2805(or)S2923(more)S(groups.)298 3164 A3521(One)S3724(of)S3843(these)S(groups)273 4085 A4393(is)S(distinguished)535 4495 A5065(from)S5256 V1330(others)S1604(and)S1777(used)S1989(in)S2095(implementing)S(accounting)441 2680 A(facilities.)373 3148 A3573(The)S(positive)318 3757 A4102(integer)S(corresponding)575 4409 A5011(to)S5116(this)S5376 V(distinguished)535 1330 A(group)234 1895 A2159(is)S2256(termed)S2566(the)S2719(real)S(group)234 2901 A3165(ID.)S3352(\(Under)S3668(standard)S4039(Minix)S4314(this)S4490(is)S4588(the)S4742(only)S(group)234 4951 A5216(a)S5496 V1330(process)S1657(can)S1822(be)S1942(a)S2012(member)S2367(of.\))S5664 V1330(All)S1494(processes)S1915(have)S2140(a)S2220(real)S2407(user)S2610(ID)S2752(and)S2932(real)S(group)234 3119 A3388(ID.)S3580(These)S3856(are)S(initialized)403 4015 A4453(from)S4684(the)S4842(equivalent)S5784 V1330(attributes)S1730(of)S1839(the)S1987(process)S2314(that)S2490(created)S2807(it.)S5952 V1080(Effective)S1476(User)S1692(Id,)S1826(Effective)S(Group)257 2222 A2504(Id,)S2638(and)S(Access)286 2808 A(Groups)296 3119 A6072 V(Access)286 1330 A1642(to)S1746(system)S2051(resources)S2458(is)S(governed)374 2551 A2951(by)S3077(three)S3305(values:)S3616(the)S3765(effective)S4145(user)S4339(ID,)S4497(the)S4646(effective)S(group)234 5027 A6192 V1330(ID,)S1487(and)S1657(the)S(group)234 1805 A(access)258 2064 A2347(list.)S6360 V1330(The)S1527(effective)S1921(user)S2129(ID)S2276(and)S2461(effective)S(group)234 2855 A3129(ID)S3276(are)S(initially)313 3440 A3793(the)S3957(process's)S4373(real)S4566(user)S4775(ID)S4923(and)S5109(real)S6480 V(group)234 1330 A1594(ID)S1731(respectively.)S2298(Either)S2575(may)S2778(be)S2903(modified)S(through)312 3296 A3638(execution)S4059(of)S4173(a)S(set-user-ID)455 4248 A4733(or)S(set-group-)414 4847 A6600 V1330(ID)S1462(file)S1622(\(possibly)S2015(by)S2140(one)S2310(its)S2430(ancestors\))S2864(\(see)S10 B3052(execve)S10 R3332(\(2\)\).)S6768 V1330(The)S(group)234 1516 A(access)258 1779 A2066(list)S2218(is)S2314(an)S(additional)402 2438 A2869(set)S3010(of)S(group)234 3123 A3386(ID's)S3595(used)S3808(only)S4015(in)S4122(determining)S4637(resource)S(acces-)253 5008 A6888 V(sibility.)304 1330 A(Access)286 1695 A2017(checks)S2327(are)S2487(performed)S2943(as)S3063(described)S3485(below)S3767(in)S3881(``File)S(Access)286 4142 A4464(Permissions''.)S5104(The)S7008 V1330(maximum)S1786(number)S2142(of)S(additional)402 2275 A(group)234 2726 A3009(ID's)S3238(is)S3355(NGROUPS_MAX.)S4211(For)S4401(Minix)S4696(this)S4891(is)S5008(0,)S5133(but)S7128 V1330(Minix-vmd)S(supports)340 1822 A2197(a)S2277(list)S2435(of)S2554(up)S2689(to)S2802(16)S(additional)402 2937 A(group)234 3374 A3642(ID's.)S3906(\(Also)S(known)273 4164 A4471(as)S(``supplemental'')672 4589 A7248 V(group)234 1330 A1589(ID's.\))S7903 V720(September)S1176(13,)S(1996)200 1326 A2669(\()S2711(June)S2920(30,)S(1986)200 3070 A3278(\))S4990(Page)S5211(4)S8143 VEP%%Page: 5 5BP/slant 0 def/height 0 def480 V10 R720(INTRO)S1037(\()S1079(2)S1137(\))S2696(Eighth)S(Edition)296 2989 A4810(INTRO)S5127(\()S5169(2)S5227(\))S960 V1080(Super-user)S1080 V1330(A)S1435(process)S1769(is)S(recognized)442 1868 A2342(as)S2458(a)S10 I2535(super-user)S10 R2997(process)S3331(and)S3508(is)S3607(granted)S3941(special)S4254(privileges)S4684(if)S4779(its)S4907(effective)S1200 V1330(user)S1523(ID)S1655(is)S1747(0.)S1368 V1080(Descriptor)S1488 V1330(An)S1492(integer)S1811(assigned)S2196(by)S2335(the)S2497(system)S2815(when)S3072(a)S3156(\256le)S3324(or)S3447(device)S3749(is)S3855(referenced)S4321(by)S10 B4461(open)S10 R4668(\(2\),)S10 B(dup)168 4851 A10 R5019(\(2\))S5177(or)S1608 V10 B1330(fcntl)S10 R1527(\(2\))S1681(which)S1963(uniquely)S2350(identi\256es)S2755(an)S(access)258 2886 A3180(path)S3389(to)S3503(that)S3690(\256le)S3854(or)S3973(device)S4271(from)S4502(a)S4582(given)S4840(process)S5177(or)S1728 V1330(any)S1500(of)S1609(its)S1729(children.)S1896 V1080(File)S1262(Descriptor)S2016 V1330(Older,)S1610(and)S1780(often)S2012(used)S2221(name)S2464(for)S2607(a)S2677(descriptor.)S2184 V1080(File)S1262(Name)S2304 V1330(Names)S1642(consisting)S2081(of)S2197(up)S2329(to)S2439(NAME_MAX)S3053(characters)S3495(may)S3700(be)S3827(used)S4043(to)S4153(name)S4404(an)S4532(ordinary)S4906(\256le,)S5093(spe-)S2424 V1330(cial)S1510(\256le,)S1697(or)S1814(directory.)S2261(NAME_MAX)S2876(is)S2976(the)S3132(maximum)S3572(of)S3689(the)S3845(maximum)S4285(\256le)S4447(name)S4698(lengths)S5021(of)S5138(the)S2544 V(supported)396 1330 A1753(\256le)S1909(systems.)S2304(Excess)S2611(characters)S3048(are)S(ignored)307 3199 A3533(when)S3779(too)S(long)178 3935 A4141(\256le)S4298(names)S4583(are)S4735(used)S4947(for)S5093(\256les)S2664 V1330(in)S1437(a)S1511(given)S1763(\256le)S1921(system.)S2279(The)S2465(maximum)S2901(\256le)S3059(name)S3306(length)S3586(of)S3699(the)S3851(V1)S4003(and)S4176(V2)S4327(\256le)S4484(systems)S4830(is)S4925(14)S5053(char-)S2784 V1330(acters.)S1641(The)S1823(Minix-vmd)S2305("\257ex")S2563(variants)S2907(of)S3016(V1)S3164(and)S3334(V2)S3482(have)S3697(a)S3767(60)S3892(character)S4288(maximum.)S2952 V1330(The)S1513(characters)S1949(in)S2053(a)S2124(file)S2285(name)S2529(may)S2728(assume)S3050(any)S3222(value)S3467(representable)S4032(in)S4137(eight)S4365(bits)S4537(excluding)S4960(0)S5037(\(null\))S3072 V1330(and)S1500(the)S1648(ASCII)S1937(code)S2152(for)S2295(/)S2348(\(slash\).)S3240 V1330(Note)S1551(that)S1727(it)S1808(is)S1900(generally)S2300(unwise)S2610(to)S2713(use)S2872(one)S3042(of)S3151(\\'"<>\(\);\304$\303&*|{}[]?)S3989(as)S4098(part)S4280(of)S4389(file)S4549(names)S(because)319 4832 A5177(of)S3360 V1330(the)S1478(special)S1783(meaning)S2154(attached)S2515(to)S2618(these)S2850(characters)S3285(by)S3410(the)S3558(shell.)S3528 V1080(Path)S1284(Name)S3648 V1330(A)S1432(path)S1635(name)S1883(is)S1980(a)S2055(null-terminated)S2706(character)S3107(string)S3366(starting)S3698(with)S3907(an)S4032(optional)S4391(slash)S4622(\(/\),)S4773(followed)S5161(by)S3768 V1330(zero)S1532(or)S1644(more)S1879(directory)S2271(names)S2556(separated)S2965(by)S3092(slashes,)S3429(optionally)S3863(followed)S4248(by)S4375(a)S4447(\256le)S4603(name.)S4898(The)S5082(total)S3888 V1330(length)S1606(of)S1715(a)S1785(path)S1983(name)S2226(must)S2446(be)S2566(less)S2742(than)S2940(PATH_MAX)S3514(characters)S(\(255)184 3949 A4158(as)S4267(distributed.\))S4056 V1330(If)S1430(a)S1507(path)S1713(name)S1964(begins)S2259(with)S2471(a)S2549(slash,)S2808(the)S2964(path)S3170(search)S3461(begins)S3756(at)S3862(the)S10 I4018(root)S10 R4218(directory.)S4665(Otherwise,)S5138(the)S4176 V1330(search)S1619(begins)S1912(from)S2138(the)S2291(current)S2607(working)S2972(directory.)S3416(A)S3519(slash)S3750(by)S3880(itself)S4112(names)S4399(the)S4552(root)S4744(directory.)S5188(A)S4296 V1330(null)S1511(pathname)S1927(is)S(illegal,)277 2019 A2321(use)S2480(".")S2612(to)S2715(refer)S2932(to)S3035(the)S3183(current)S3494(working)S3854(directory.)S4464 V1080(Directory)S4584 V1330(A)S1432(directory)S1825(is)S1922(a)S1997(special)S2307(type)S2510(of)S2624(\256le)S2783(that)S2964(contains)S3329(entries)S3628(that)S3809(are)S3963(references)S4409(to)S4517(other)S4754(\256les.)S5002(Direc-)S4704 V1330(tory)S1535(entries)S1847(are)S2014(called)S2298(links.)S2586(By)S(convention,)471 2746 A3260(a)S3348(directory)S3755(contains)S4133(at)S4249(least)S4477(two)S4670(links,)S4932(.)S4999(and)S(..,)75 5186 A4824 V1330(referred)S1679(to)S1785(as)S10 I1897(dot)S10 R2053(and)S10 I2226(dot-dot)S10 R2544(respectively.)S3109(Dot)S3288(refers)S3547(to)S3654(the)S3806(directory)S4199(itself)S4430(and)S4604(dot-dot)S4923(refers)S5183(to)S4944 V1330(its)S1450(parent)S1727(directory.)S5112 V1080(Root)S1300(Directory)S1712(and)S1882(Current)S2215(Working)S2597(Directory)S5232 V1330(Each)S1560(process)S1890(has)S2052(associated)S2494(with)S2701(it)S2785(a)S2858(concept)S3199(of)S3312(a)S3386(root)S3577(directory)S3970(and)S4144(a)S4218(current)S4533(working)S4897(directory)S5352 V1330(for)S1477(the)S1629(purpose)S1976(of)S2089(resolving)S2492(path)S2694(name)S2941(searches.)S3362(A)S3464(process's)S3868(root)S4059(directory)S4451(need)S4669(not)S4825(be)S4948(the)S5099(root)S5472 V1330(directory)S1719(of)S1828(the)S1976(root)S2163(\256le)S2317(system.)S5640 V1080(File)S(Access)286 1262 A1573(Permissions)S5760 V1330(Every)S1597(\256le)S1752(in)S1856(the)S2005(\256le)S2160(system)S2465(has)S2625(a)S2696(set)S2834(of)S(access)258 2944 A3228(permissions.)S3784(These)S4051(permissions)S4558(are)S4709(used)S4920(in)S5025(deter-)S5880 V1330(mining)S1647(whether)S2005(a)S2083(process)S2417(may)S2622(perform)S2979(a)S3056(requested)S3474(operation)S3886(on)S4018(the)S4173(\256le)S4334(\(such)S4584(as)S4700(opening)S5055(a)S5132(\256le)S6000 V1330(for)S(writing\).)350 1492 A(Access)286 1911 A2241(permissions)S2765(are)S2933(established)S3424(at)S3541(the)S3709(time)S3933(a)S4023(\256le)S4197(is)S4309(created.)S4696(They)S4948(may)S5166(be)S6120 V1330(changed)S1690(at)S1788(some)S2025(later)S2230(time)S(through)312 2434 A2771(the)S10 B2919(chmod)S10 R3210(\(2\))S3353(call.)S6288 V1330(File)S(access)258 1512 A1795(is)S1887(broken)S2191(down)S(according)397 2439 A2861(to)S2965(whether)S3316(a)S3387(file)S3548(may)S3747(be:)S3896(read,)S(written,)311 4121 A4458(or)S4568(executed.)S5002(Direc-)S6408 V1330(tory)S1517(files)S1716(use)S1875(the)S2023(execute)S2356(permission)S2822(to)S2925(control)S3235(if)S3322(the)S3470(directory)S3859(may)S4057(be)S4177(searched.)S6576 V1330(File)S(access)258 1520 A1811(permissions)S2324(are)S2481(interpreted)S2951(by)S3084(the)S3240(system)S3552(as)S3669(they)S3876(apply)S4133(to)S4245(three)S4481(different)S4863(classes)S5177(of)S6696 V1330(users:)S1610(the)S1778(owner)S2075(of)S2204(the)S2372(file,)S2577(those)S2834(users)S3086(in)S3209(the)S3377(file's)S(group,)259 3630 A(anyone)290 3934 A4269(else.)S4521(Every)S4807(file)S4987(has)S5166(an)S6816 V1330(independent)S1850(set)S1991(of)S(access)258 2104 A2391(permissions)S2900(for)S(each)185 3047 A3262(of)S3376(these)S3613(classes.)S3973(When)S4243(an)S(access)258 4368 A4656(check)S4921(is)S5018(made,)S6936 V1330(the)S1479(system)S1784(decides)S2111(if)S2198(permission)S(should)267 2664 A2956(be)S3076(granted)S3403(by)S3528(checking)S3916(the)S(access)258 4064 A4347(information)S4847(applicable)S7056 V1330(to)S1433(the)S1581(caller.)S7224 V1330(Read,)S1587(write,)S1845(and)S2015(execute/search)S2634(permissions)S3139(on)S3264(a)S3334(file)S3494(are)S3643(granted)S3970(to)S4073(a)S4143(process)S4470(if:)S7392 V1330(The)S1512(process's)S1912(effective)S2291(user)S2484(ID)S2616(is)S2708(that)S2884(of)S2993(the)S3141(super-user.)S7903 V720(Page)S941(5)S2669(\()S2711(June)S2920(30,)S(1986)200 3070 A3278(\))S4455(September)S4911(13,)S(1996)200 5061 A8143 VEP%%Page: 6 6BP/slant 0 def/height 0 def480 V10 R720(INTRO)S1037(\()S1079(2)S1137(\))S2696(Eighth)S(Edition)296 2989 A4810(INTRO)S5127(\()S5169(2)S5227(\))S960 V1330(The)S1518(process's)S1924(effective)S2309(user)S2508(ID)S2646(matches)S3007(the)S3161(user)S3360(ID)S3498(of)S3613(the)S3767(owner)S4050(of)S4165(the)S4319(file)S4485(and)S4661(the)S4815(owner)S5098(per-)S1080 V1330(missions)S1706(allow)S1955(the)S(access.)283 2103 A1248 V1330(The)S1512(process's)S1912(effective)S2291(user)S2484(ID)S2617(does)S2827(not)S2981(match)S3253(the)S3402(user)S3596(ID)S3729(of)S3839(the)S3988(owner)S4266(of)S4376(the)S4525(file,)S4711(and)S4882(either)S5138(the)S1368 V1330(process's)S1733(effective)S(group)234 2115 A2376(ID)S2510(matches)S2867(the)S(group)234 3017 A3278(ID)S3412(of)S3523(the)S3673(file,)S3860(or)S3971(the)S(group)234 4121 A4382(ID)S4516(of)S4627(the)S4777(file)S4939(is)S5033(in)S5138(the)S1488 V1330(process's)S(group)234 1730 A(access)258 1989 A2272(list,)S2445(and)S2615(the)S(group)234 2763 A3022(permissions)S3527(allow)S3776(the)S(access.)283 3924 A1656 V1330(Neither)S1666(the)S1822(effective)S2209(user)S2410(ID)S2550(nor)S2717(effective)S(group)234 3104 A3371(ID)S3511(and)S(group)234 3689 A(access)258 3956 A4247(list)S4404(of)S4522(the)S4679(process)S5015(match)S1776 V1330(the)S(corresponding)575 1484 A2090(user)S2288(ID)S2425(and)S(group)234 2600 A2864(ID)S3001(of)S3115(the)S3268(file,)S3458(but)S3616(the)S3769(permissions)S4279(for)S4427(``other)S4732(users'')S5037(allow)S1896 V(access.)283 1330 A2064 V1330(Otherwise,)S1795(permission)S2261(is)S2353(denied.)S2232 V9 R720(S)S722(SE)S774(EE)S832(E)S928(A)S930(AL)S998(LS)S1056(SO)S1108(O)S2352 V10 B1080(intro)S10 R1293(\(3\),)S10 B(strerror)348 1461 A10 R1809(\(3\).)S7903 V720(September)S1176(13,)S(1996)200 1326 A2669(\()S2711(June)S2920(30,)S(1986)200 3070 A3278(\))S4990(Page)S5211(6)S8143 VEP%%Trailer%%DocumentFonts: Times-Roman Times-Bold Times-Italic%%Pages: 6⌨️ 快捷键说明
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