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(While the GNU operating system will most lik)97 325.8 R .697
(ely include a v)-.1 F .697(ersion of the Berk)-.15 F(ele)-.1 E 3.197
(ys)-.15 G .696(hell csh, Bash)-3.197 F .015(will be the def)72 337.8 R
.015(ault shell.)-.1 F(Lik)5.015 E 2.515(eo)-.1 G .015(ther GNU softw)
-2.515 F .016(are, Bash is quite portable.)-.1 F .016
(It currently runs on nearly e)5.016 F -.15(ve)-.25 G(ry).15 E -.15(ve)
72 349.8 S .523(rsion of).15 F F4(UNIX)3.023 E F3 .523(and a fe)3.023 F
3.023(wo)-.25 G .523
(ther operating systems \255 an independently-supported port e)-3.023 F
.523(xists for OS/2, and)-.15 F .706
(there are rumors of ports to DOS and W)72 361.8 R(indo)-.4 E .706
(ws NT)-.25 F 5.706(.P)-.74 G .706(orts to)-5.706 F F5(UNIX)3.206 E F3
(-lik)A 3.206(es)-.1 G .706(ystems such as QNX and Minix)-3.206 F
(are part of the distrib)72 373.8 Q(ution.)-.2 E .405
(The original author of Bash w)97 389.4 R .405(as Brian F)-.1 F .405
(ox, an emplo)-.15 F .405(yee of the Free Softw)-.1 F .405(are F)-.1 F
2.905(oundation. The)-.15 F(cur)2.905 E(-)-.2 E(rent de)72 401.4 Q -.15
(ve)-.25 G(loper and maintainer is Chet Rame).15 E 1.3 -.65(y, a v)-.15
H(olunteer who w).45 E(orks at Case W)-.1 E(estern Reserv)-.8 E 2.5(eU)
-.15 G(ni)-2.5 E -.15(ve)-.25 G(rsity).15 E(.)-.65 E F2 2.5(2. What')72
425.4 R 2.5(sP)-.37 G(OSIX, anyway?)-2.5 E F1(POSIX)97 441 Q F3 .343
(is a name originally coined by Richard Stallman for a f)2.843 F .343
(amily of open system standards based)-.1 F(on)72 453 Q F5(UNIX)3.24 E
F3 5.74(.T)C .74(here are a number of aspects of)-5.74 F F5(UNIX)3.24 E
F3 .74(under consideration for standardization, from the basic)3.24 F
.192(system services at the system call and C library le)72 465 R -.15
(ve)-.25 G 2.692(lt).15 G 2.692(oa)-2.692 G .192
(pplications and tools to system administration and)-2.692 F 2.5
(management. Each)72 477 R(area of standardization is assigned to a w)
2.5 E(orking group in the 1003 series.)-.1 E 2.814
(The POSIX Shell and Utilities standard has been de)97 492.6 R -.15(ve)
-.25 G 2.814(loped by IEEE W).15 F 2.813(orking Group 1003.2)-.8 F .254
(\(POSIX.2\).\210 It concentrates on the command interpreter interf)72
504.6 R .253(ace and utility programs commonly e)-.1 F -.15(xe)-.15 G
(cuted).15 E 1.112(from the command line or by other programs.)72 516.6
R 1.112(An initial v)6.112 F 1.113
(ersion of the standard has been appro)-.15 F -.15(ve)-.15 G 3.613(da)
.15 G(nd)-3.613 E .365(published by the IEEE, and w)72 528.6 R .365
(ork is currently underw)-.1 F .365(ay to update it.)-.1 F .365
(There are four primary areas of w)5.365 F(ork)-.1 E
(in the 1003.2 standard:)72 540.6 Q 21.5<8341>72 556.2 S .835
(spects of the shell')-21.5 F 3.335(ss)-.55 G .835
(yntax and command language.)-3.335 F 3.335(An)5.835 G .835
(umber of special b)-3.335 F .835(uiltins such as)-.2 F F2(cd)3.335 E F3
(and)3.335 E F2(exec)97 568.2 Q F3 .545(are being speci\214ed as part o\
f the shell, since their functionality usually cannot be implemented)
3.046 F(by a separate e)97 580.2 Q -.15(xe)-.15 G(cutable;).15 E 21.5
<8341>72 595.8 S .926
(set of utilities to be called by shell scripts and applications.)
-18.074 F .927(Examples are programs lik)5.927 F(e)-.1 E F1 .927
(sed, tr)3.427 F(,)-1.11 E F3(and)97 607.8 Q F1(awk.)2.797 E F3 .297
(Utilities commonly implemented as shell b)5.297 F .296
(uiltins are described in this section, such as)-.2 F F2(test)2.796 E F3
(and)97 619.8 Q F2(kill)3.422 E F3 5.922(.A)C 3.422(ne)-5.922 G .922
(xpansion of this section')-3.572 F 3.423(ss)-.55 G .923
(cope, termed the User Portability Extension, or UPE, has)-3.423 F
(standardized interacti)97 631.8 Q .3 -.15(ve p)-.25 H(rograms such as)
.15 E F1(vi)2.5 E F3(and)2.5 E F1(mailx;)2.5 E F3 21.5<8341>72 647.4 S
.288(group of functional interf)-18.712 F .287(aces to services pro)-.1
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(ibrary function.)-3.289 F .789(There are functions to perform shell w)
5.789 F .789(ord e)-.1 F .79(xpansions, perform \214lename e)-.15 F
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(*An earlier v)72 703.2 Q
(ersion of this article appeared in The Linux Journal.)-.12 E(\210IEEE,)
72 715 Q/F7 8/Times-Italic@0 SF 1.231(IEEE Standar)3.231 F 3.231(df)
-.296 G 1.231(or Information T)-3.231 F(ec)-.736 E(hnolo)-.12 E 1.231
(gy -- P)-.08 F 1.231(ortable Oper)-.64 F 1.232
(ating System Interface \(POSIX\) P)-.12 F 1.232(art 2:)-.64 F
(Shell and Utilities)72 725 Q F4 2(,1)C(992.)-2 E EP
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/F0 10/Times-Roman@0 SF(-2-)282.17 48 Q 21.5<8341>72 84 S
(suite of \231de)-19 E -.15(ve)-.25 G(lopment\232 utilities such as).15
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-.15 E F1(cc)2.5 E F0(\), and)A F1(yacc.)2.5 E F0 .483
(Bash is concerned with the aspects of the shell')97 99.6 R 2.983(sb)
-.55 G(eha)-2.983 E .484(vior de\214ned by POSIX.2.)-.2 F .484
(The shell command)5.484 F 1.439
(language has of course been standardized, including the basic \215o)72
111.6 R 3.938(wc)-.25 G 1.438(ontrol and program e)-3.938 F -.15(xe)-.15
G 1.438(cution con-).15 F 1.284
(structs, I/O redirection and pipelining, ar)72 123.6 R 1.284
(gument handling, v)-.18 F 1.284(ariable e)-.25 F 1.284
(xpansion, and quoting.)-.15 F(The)6.285 E F1(special)3.785 E F0 -.2(bu)
72 135.6 S .676
(iltins, which must be implemented as part of the shell to pro).2 F .676
(vide the desired functionality)-.15 F 3.176(,a)-.65 G .676
(re speci\214ed)-3.176 F .7(as being part of the shell; e)72 147.6 R .7
(xamples of these are)-.15 F/F2 10/Times-Bold@0 SF -2.3 -.15(ev a)3.201
H(l).15 E F0(and)3.201 E F2(export)3.201 E F0 5.701(.O)C .701
(ther utilities appear in the sections of)-5.701 F .256(POSIX.2 not de)
72 159.6 R -.2(vo)-.25 G .256(ted to the shell which are commonly \(and\
 in some cases must be\) implemented as b).2 F(uiltin)-.2 E .213
(commands, such as)72 171.6 R F2 -.18(re)2.713 G(ad).18 E F0(and)2.713 E
F2(test)2.713 E F0 5.213(.P)C .213
(OSIX.2 also speci\214es aspects of the shell')-5.213 F 2.713(si)-.55 G
(nteracti)-2.713 E .513 -.15(ve b)-.25 H(eha).15 E .214(vior as part)-.2
F .598(of the UPE, including job control and command line editing.)72
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(-style line edit-)B(ing commands ha)72 195.6 Q .3 -.15(ve b)-.2 H
(een standardized;).15 E F1(emacs)2.5 E F0
(editing commands were left out due to objections.)2.5 E 1.128
(While POSIX.2 includes much of what the shell has traditionally pro)97
211.2 R 1.129(vided, some important things)-.15 F(ha)72 223.2 Q .344
-.15(ve b)-.2 H .044(een omitted as being \231be).15 F .044
(yond its scope.)-.15 F 5.043<9a54>-.7 G .043
(here is, for instance, no mention of a dif)-5.043 F .043
(ference between a)-.25 F F1(lo)72 235.2 Q(gin)-.1 E F0 1.445
(shell and an)3.945 F 3.945(yo)-.15 G 1.445(ther interacti)-3.945 F
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(No \214x)6.446 F(ed)-.15 E(startup \214les are de\214ned, either \255 \
the standard does not mention)72 247.2 Q F1(.pr)2.5 E(o\214le)-.45 E F0
(.)A F2 2.5(3. Basic)72 271.2 R(Bash featur)2.5 E(es)-.18 E F0 1.448
(Since the Bourne shell pro)97 286.8 R 1.448
(vides Bash with most of its philosophical underpinnings, Bash inherits)
-.15 F .64(most of its features and functionality from sh.)72 298.8 R
.641(Bash implements all of the traditional sh \215o)5.641 F 3.141(wc)
-.25 G .641(ontrol con-)-3.141 F .8(structs \()72 310.8 R F1(for)A F0(,)
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.799(of the Bourne shell b)3.3 F .799
(uiltins, including those not speci\214ed in the POSIX.2)-.2 F .536
(standard, appear in Bash.)72 322.8 R(Shell)5.536 E F1(functions)3.036 E
F0 3.036(,i)C .536(ntroduced in the SVR2 v)-3.036 F .537
(ersion of the Bourne shell, are similar)-.15 F .779
(to shell scripts, b)72 334.8 R .779
(ut are de\214ned using a special syntax and are e)-.2 F -.15(xe)-.15 G
.779(cuted in the same process as the calling).15 F 2.841(shell. Bash)72
346.8 R .341(has shell functions which beha)2.841 F .641 -.15(ve i)-.2 H
2.841(naf).15 G .341(ashion upw)-2.941 F .342
(ard-compatible with sh functions.)-.1 F .342(There are)5.342 F 1.447
(certain shell v)72 358.8 R 1.446
(ariables that Bash interprets in the same w)-.25 F 1.446
(ay as sh, such as)-.1 F F2(PS1)3.946 E F0(,)A F2(IFS)3.946 E F0 3.946
(,a)C(nd)-3.946 E F2 -.74(PA)3.946 G(TH)-.21 E F0 6.446(.B)C(ash)-6.446
E 1.423(implements essentially the same grammar)72 370.8 R 3.924(,p)-.4
G 1.424(arameter and v)-3.924 F 1.424(ariable e)-.25 F 1.424
(xpansion semantics, redirection, and)-.15 F 1.06
(quoting as the Bourne shell.)72 382.8 R 1.06(Where dif)6.06 F 1.06
(ferences appear between the POSIX.2 standard and traditional sh)-.25 F
(beha)72 394.8 Q(vior)-.2 E 2.5(,B)-.4 G(ash follo)-2.5 E(ws POSIX.)-.25
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(escendent of the Bourne shell written at A)-4.108 F 1.609
(T&T Bell Laboratories by)-1.11 F(Da)72 422.4 Q 1.059(vid K)-.2 F 3.559
(orn\207. It)-.35 F(pro)3.559 E 1.059
(vides a number of useful features that POSIX and Bash ha)-.15 F 1.359
-.15(ve a)-.2 H 3.558(dopted. Man).15 F 3.558(yo)-.15 G 3.558(ft)-3.558
G(he)-3.558 E(interacti)72 434.4 Q 1.312 -.15(ve f)-.25 H 1.012
(acilities in POSIX.2 ha).05 F 1.312 -.15(ve t)-.2 H 1.012
(heir roots in the ksh: for e).15 F 1.013
(xample, the POSIX and ksh job control)-.15 F -.1(fa)72 446.4 S .513
(cilities are nearly identical. Bash includes features from the K).1 F
.513(orn Shell for both interacti)-.35 F .813 -.15(ve u)-.25 H .513
(se and shell).15 F 3.905(programming. F)72 458.4 R 1.405
(or programming, Bash pro)-.15 F 1.405(vides v)-.15 F 1.405
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470.4 S .398(iltin, the ability to remo).2 F .698 -.15(ve s)-.15 H .398
(ubstrings from v).15 F .398
(ariables based on patterns, and shell arithmetic.)-.25 F F2(RANDOM)
5.397 E F0 -.15(ex)72 482.4 S .489
(pands to a random number each time it is referenced; assigning a v).15
F .49(alue to)-.25 F F2(RANDOM)2.99 E F0 .49(seeds the random)2.99 F
.055(number generator)72 494.4 R(.)-.55 E F2(REPL)5.055 E(Y)-.92 E F0
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F F2 -.18(re)2.554 G(ad).18 E F0 -.2(bu)2.554 G .054(iltin when no v).2
F .054(ariable names are sup-)-.25 F .742(plied as ar)72 506.4 R 3.243
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(iltin is used to de\214ne v).2 F .743(ariables and gi)-.25 F 1.043 -.15
(ve t)-.25 H .743(hem attrib).15 F .743(utes such as)-.2 F F2 -.18(re)
3.243 G(ad-).18 E(only)72 518.4 Q F0 5.512(.B)C .512
(ash arithmetic allo)-5.512 F .512(ws the e)-.25 F -.25(va)-.25 G .511
(luation of an e).25 F .511
(xpression and the substitution of the result.)-.15 F .511(Shell v)5.511
F(ari-)-.25 E .222
(ables may be used as operands, and the result of an e)72 530.4 R .222
(xpression may be assigned to a v)-.15 F 2.722(ariable. Nearly)-.25 F
.222(all of)2.722 F(the operators from the C language are a)72 542.4 Q
-.25(va)-.2 G(ilable, with the same precedence rules:).25 E/F3 10
/Courier@0 SF 6($e)97 560.4 S(cho $\(\(3 + 5 * 32\)\))-6 E(163)97 572.4
Q F0 -.15(Fo)72 594 S 3.24(ri).15 G(nteracti)-3.24 E 1.04 -.15(ve u)-.25
H .74(se, Bash implements ksh-style aliases and b).15 F .74
(uiltins such as)-.2 F F2(fc)3.24 E F0 .74(\(discussed belo)3.24 F .74
(w\) and)-.25 F F2(jobs)3.24 E F0(.)A .291(Bash aliases allo)72 606 R
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-2.791 F .568(for a)72 618 R/F4 9/Times-Roman@0 SF(UNIX)3.068 E F0 .568
(command name \()3.068 F F3 .568(alias del=rm)B F0 .568(\), to e)B .567
(xpand a single w)-.15 F .567(ord to a comple)-.1 F 3.067(xc)-.15 G .567
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(hile at Berk)-2.792 F(ele)-.1 E 1.592 -.65(y, i)-.15 H 2.792(sw).65 G
.292(idely used and quite popular)-2.792 F 1.499(for its interacti)72
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(includes a csh-compatible history e)3.999 F 1.5
(xpansion mechanism \(\231! history\232\),)-.15 F .019(brace e)72 681.6
R .018(xpansion, access to a stack of directories via the)-.15 F F2
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2.518 E F0 -.2(bu)2.518 G .018(iltins, and tilde e).2 F(xpansion,)-.15 E
1.293(to generate users' home directories.)72 693.6 R -.35(Ti)6.294 G
1.294(lde e).35 F 1.294(xpansion has also been adopted by both the K)
-.15 F 1.294(orn Shell and)-.35 F .32 LW 144 708.2 72 708.2 DL/F5 8
/Times-Roman@0 SF(\207Morris Bolsk)72 720 Q 2(ya)-.12 G(nd Da)-2 E
(vid K)-.16 E(orn,)-.28 E/F6 8/Times-Italic@0 SF(The K)2 E
(ornShell Command and Pr)-.32 E -.08(og)-.36 G -.12(ra).08 G
(mming Langua).12 E -.08(ge)-.08 G F5 2(,P).08 G(rentice Hall, 1989.)-2
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/F0 10/Times-Roman@0 SF(-3-)282.17 48 Q(POSIX.2.)72 84 Q .148
(There were certain areas in which POSIX.2 felt standardization w)97
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.149(xisting imple-)-.15 F 1.598(mentation pro)72 111.6 R 1.598
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-6.598 F 1.597(orking group in)-.1 F -.15(ve)-.4 G 1.597
(nted and standardized functionality in).15 F .674
(these areas, which Bash implements.)72 123.6 R(The)5.674 E/F1 10
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