From 3253a23b915df9c6e10d586a4a69181c1f1079bc Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Wed, 24 Oct 2018 00:20:34 +0200
Subject: [PATCH] Add a simplified waitpid() so that sh can wait on spawned
 commands.

---
 Kernel/Syscall.cpp  |   2 ++
 Kernel/Syscall.h    |   1 +
 Kernel/Task.cpp     |  33 ++++++++++++++++++++++++++-------
 Kernel/Task.h       |   5 +++++
 Kernel/_fs_contents | Bin 1024000 -> 1024000 bytes
 LibC/unistd.cpp     |   5 +++++
 LibC/unistd.h       |   1 +
 Userland/sh.cpp     |   2 ++
 8 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/Kernel/Syscall.cpp b/Kernel/Syscall.cpp
index ede05bda5f..a5701b452f 100644
--- a/Kernel/Syscall.cpp
+++ b/Kernel/Syscall.cpp
@@ -88,6 +88,8 @@ DWORD handle(DWORD function, DWORD arg1, DWORD arg2, DWORD arg3)
         return current->sys$getgid();
     case Syscall::PosixGetpid:
         return current->sys$getpid();
+    case Syscall::PosixWaitpid:
+        return current->sys$waitpid((pid_t)arg1);
     case Syscall::PosixExit:
         cli();
         locker.unlock();
diff --git a/Kernel/Syscall.h b/Kernel/Syscall.h
index 095fc507e7..edc24d610b 100644
--- a/Kernel/Syscall.h
+++ b/Kernel/Syscall.h
@@ -23,6 +23,7 @@ enum Function {
     PosixExit = 0x1991,
     PosixGetgid = 0x1992,
     PosixGetpid = 0x1993,
+    PosixWaitpid = 0x1994,
 };
 
 void initialize();
diff --git a/Kernel/Task.cpp b/Kernel/Task.cpp
index 075c4709a8..6c0ba1d43d 100644
--- a/Kernel/Task.cpp
+++ b/Kernel/Task.cpp
@@ -11,6 +11,9 @@
 #include "MemoryManager.h"
 
 //#define DEBUG_IO
+//#define TASK_DEBUG
+
+static const DWORD defaultStackSize = 16384;
 
 Task* current;
 Task* s_kernelTask;
@@ -169,7 +172,9 @@ Task* Task::create(const String& path, uid_t uid, gid_t gid)
 
     s_tasks->prepend(t);
     system.nprocess++;
+#ifdef TASK_DEBUG
     kprintf("Task %u (%s) spawned @ %p\n", t->pid(), t->name().characters(), t->m_tss.eip);
+#endif
     sti();
 
     return t;
@@ -206,9 +211,6 @@ Task::Task(String&& name, uid_t uid, gid_t gid)
 
     m_tss.cr3 = MemoryManager::the().pageDirectoryBase().get();
 
-    // NOTE: Each task gets 16KB of stack.
-    static const DWORD defaultStackSize = 16384;
-
     auto* region = allocateRegion(defaultStackSize, "stack");
     ASSERT(region);
     m_stackTop = region->linearAddress.offset(defaultStackSize).get() & 0xfffffff8;
@@ -287,9 +289,6 @@ Task::Task(void (*e)(), const char* n, IPC::Handle h, RingLevel ring)
         m_tss.eip = codeRegion->linearAddress.get();
     }
 
-    // NOTE: Each task gets 16KB of stack.
-    static const DWORD defaultStackSize = 16384;
-
     if (isRing0()) {
         // FIXME: This memory is leaked.
         // But uh, there's also no kernel task termination, so I guess it's not technically leaked...
@@ -327,8 +326,9 @@ Task::Task(void (*e)(), const char* n, IPC::Handle h, RingLevel ring)
     s_tasks->prepend(this);
 
     system.nprocess++;
-
+#ifdef TASK_DEBUG
     kprintf("Task %u (%s) spawned @ %p\n", m_pid, m_name.characters(), m_tss.eip);
+#endif
 }
 
 Task::~Task()
@@ -359,7 +359,9 @@ void Task::dumpRegions()
 void Task::sys$exit(int status)
 {
     cli();
+#ifdef TASK_DEBUG
     kprintf("sys$exit: %s(%u) exit with status %d\n", name().characters(), pid(), status);
+#endif
 
     setState(Exiting);
 
@@ -473,6 +475,13 @@ bool scheduleNewTask()
                 continue;
             }
         }
+
+        if (task->state() == Task::BlockedWait) {
+            if (!Task::fromPID(task->waitee())) {
+                task->unblock();
+                continue;
+            }
+        }
     }
 
     auto* prevHead = s_tasks->head();
@@ -693,6 +702,16 @@ pid_t Task::sys$getpid()
     return m_pid;
 }
 
+pid_t Task::sys$waitpid(pid_t waitee)
+{
+    if (!Task::fromPID(waitee))
+        return -1;
+    m_waitee = waitee;
+    block(BlockedWait);
+    yield();
+    return m_waitee;
+}
+
 bool Task::acceptsMessageFrom(Task& peer)
 {
     return !ipc.msg.isValid() && (ipc.src == IPC::Handle::Any || ipc.src == peer.handle());
diff --git a/Kernel/Task.h b/Kernel/Task.h
index 06c8dc8212..7427daee80 100644
--- a/Kernel/Task.h
+++ b/Kernel/Task.h
@@ -37,6 +37,7 @@ public:
         Terminated = 6,
         Crashing = 7,
         Exiting = 8,
+        BlockedWait = 9,
     };
 
     enum RingLevel {
@@ -97,6 +98,7 @@ public:
     void sys$sleep(DWORD ticks);
     void sys$exit(int status);
     int sys$spawn(const char* path);
+    pid_t sys$waitpid(pid_t);
 
     struct
     {
@@ -116,6 +118,8 @@ public:
     void didSchedule() { ++m_timesScheduled; }
     dword timesScheduled() const { return m_timesScheduled; }
 
+    pid_t waitee() const { return m_waitee; }
+
 private:
     friend class MemoryManager;
 
@@ -145,6 +149,7 @@ private:
     int m_error { 0 };
     void* m_kernelStack { nullptr };
     dword m_timesScheduled { 0 };
+    pid_t m_waitee { -1 };
 
     struct Region {
         Region(LinearAddress, size_t, RetainPtr<Zone>&&, String&&);
diff --git a/Kernel/_fs_contents b/Kernel/_fs_contents
index e74551456e35e00dd6d24e4cef5777a3c55b7928..70277d8a7b6b46678562f84003bee4969fa4821e 100644
GIT binary patch
delta 12524
zcmZoTVApWKZUYYs<MheAEb^S!XP%D+Vg1dfEY6HfWy~8H+n6SC@Gwr_%**kUpNYS2
zBBKT8|7HgU1_p)$|0gmUZ?2K(kmR!vXJF{EJ_pu&edgpzra_Zaj24)d2s1F096bva
zJ|7Lz#lXPGzy)D2FfuSO*fTLOI506VI5IIXI59CWI8Qb-(B7P4tiWW-Ai}`l^bBSy
zcI_@q3=FPJ3=D2e3=Hl}3=AG%?N3Z?<_VYZL98(WQyL5k4D#EJbr=t@v2-5VF=cvu
z4TsTmd1FRNMuzS8jX0(=PCpmJs4)Fs9f!d5e=&>#lUIEVnjT=vs5jZ_lUF^+$wCYQ
z3?5*^7#KJh7#M^YxES)G{2xppJ}ZMiln;^TW(Y&!b27w2`Ep?WLJTQTz66-h$B+r-
zyMp;l40#Z~7J~va$O3kTGKc^J$a6vrf(*4#zBE_^4@1-RL^DQz_VUEcl7h^X>FdoH
z-Rcz?7-Se27?|W37?eS@0t16K0|NsiKLdjSh%e6o_7|f70|P4)0|TQF1A_sS4u{ei
zP<k7b4g~2JWMGhh^1YyR8I*2;(#JsI0y2;tWRV&q;FwglbFJafV}iTVa2?0$>3M}5
zc9R~faH?=KFlaC^Fvw0nXvLV%>B9|irR?;*>pA47M_4mzaMr-ZcsFp!PhVlpxPWsF
zH^gw+>47$k#f)5&86OJ^9sxO%fq{Vy8cKhsAGBc<7rlxm%+1cgAP3T5d69vEfs=uO
z0i41a7#Oy|Oa%uo0|N^K#Fj@;6O5n+Yfe7<R9x^ERFnxS>M}jimQmdD8=9eexEUCB
zfPBcnz#z(iFqD@Olsgz0VA>Zzv~x0|x~YT*p<NtFyDXaaKhqiQ7{vv(p~B2iNAXM#
z1PL25LVSWIYz9>gRm=cUJ$-^5qW~`t2Lr<dCI$vj;+2`cP>WHTbq*H;L&x;M%^b?C
zI=l=FZj&AV%%5~cL3oBB!~j_4Q(;h^Zk)hT#K=8;SptU*<GJaN6F96HCry`6<jB-%
z{_($5C?Fs_qn?3*;l-c-|Nl215qQlCW*uvN@$dhCh^XO#*ZteqFW_inQv~H<Nd|_q
z4TlXcHP{F+lrTHJ{@!`vaOa^NjbQQV0Wys8(`VOk)J}hr!67r<zn0_VG!sU@>2-A+
z4b$(LFbaV3y20dC9~Gwi)pI0GKTyw6!00yJuz^Dzn%#vM5+J^SW_KQjUML@u-Psw^
zp?pYo=Y?fgsCsUOQm8zn_z+>JhVnrnD8wMj&;;c}vcCXBJA`k=ki-be?ko&F5CLfR
z=VX`y<wLT+FvDypACmp~7#2+L%;E54FDS}SPAx8;eD|I>Jd?f8;qa?hV_*;fB~n2K
z1}P{l56YP;3=AL|lv7ned|d_xQ;@t61A`Taufo9K1EQH2z(p35CIdqeRK6S}uEM}D
z5z3zi<*$SCH$(X+7#JApnG_iqSU^ckh=D<jk%56pn}I<YM5{9}7(>M^KztPj1}6}$
z#K7POqCsUl$UtFe86^rWqeK}Pz-5#u0|U5>5@lcjmr<e&4B#?K1X@OkGB9{CF=#U|
ziZU>O3n@_s25=!I%D@0Bq(I`}GD-)MEts^n$K`RjFv&wpQU<+})QS?l;*z4A)I1oc
zAhCS1;3MhjT&j!<rWX`)Byg7SGB7AGFfb@izgftk%$PKJ<8$HZ0!17GoKtui7#4tK
zG>bUoSr0HWFz`-S)M6BwK39#ApYiPU!XgfJP7^*zX{R`SVG)Ns<I(8{L82*e(T^a}
zr_%+CIn){7f++Fn0mU2wj9;fG7IUbx{$*!ikOmcG(-#zj?Bs)ZMsfPiVh(v$2@VDZ
z39#%3kRF5Sj3pfEj8-5@T<{hsbdicmm+6e19O8n{(S(B_s=uQN$4n0_;Sjg{j8@Xk
zfjI!Jqyr}b1_lOL@mV!}A;>a$Pzpd2ZkYbDghO1=94ZVe7e%Ij?Bo!)1f>_`vU&+0
zq+C>FU|^6$Di^)bv=@N2+q$6@t1<it?V#)gE9#@rw4dQ*U=W!8QIJtsFas(DD?{&0
ze^|;PE|`Z_v_gf8p{k)-mf_BH!!iza&O4k83?G;n7?h?bc5}$Hp5b9&SOzIkMFbca
znkPH{xxMLyg2ZBlD<bU*I*jcKI!x^fI?U|~IxOu9I;`yqI&AF<I_%38bT~|eErcMZ
z!^&MX2G!}{a#sOd?(#flU|?we!Bi&@5D+%~T>^&z<8n|DY*ioLI~7#U26axo@bCZs
z3{a---J9|M|Nn4sDct!3LLF~DBGCNfe>YfFsX$<05K5U1D#JnL07NlF4{`zCd_=(T
zz{{%t|Nr-<eu<8YkL^wW5f3V}x9?lPQO;(8t5gqeej@-c**gyhWPp4LvE)Yc5s7Hj
z!d^<DxFE4SFEvG>ATvclwNys|l!-I*(iQUa6f#Tn^z^1LT+VTtqqv|vPeHYmYa*k<
zbOAZWN1%3Jz~o;a1*V&2a|lgeP|u;j53&e`nHiL(@2}^uXOx@%zn;U8R+R-P{R%Ol
zR~BNpD~oa(RTk<vDhpM#%0dsVvQR~<EVR%n3stnrLY095rLs_EV1QH>N(>BKpiBd+
zEOZzcK#d$G4F(2NsJIoVa!_SpaE0<gnVm_MfguniuFSv?3!=%ZJiHkgQELyvm4_|^
z1E}G{D8|4b2CDW{A>}WVHl#9v*TshGI3!p=i4<IYWVLdn@PK%Ep!&s7&v5!h3l0}Z
zg>na4p(sNtlyXFc@`sm!VFLpLgYtB6g>n_GLU{zKP}V@J4rNG%atl(S+<}XNE0kZL
znnazEX}Vws2ed-r0<qOug*Z?u6drzvhm;`|iY{t};tHx8)EWIj6lR4I39e8?U!&C=
z=^P9Uil9nK6;#zAm**n<kn{)YvxvaT^XZA|9Kwtpkm?3h3nA-JfjN%>68^9voCB0N
zkm{9X;Oa&c)bIfHL1DGf8V&}A&66)a6&AFHYJk-^3E(Qj5>yc(+ouDqGC(c_HK$<q
zfm$pegJIhDK(vF>CbIS?NZLUiG??}{G}|SnPwe6l7tMhR!<?(Z#lXM`c5Wk7238Ll
zPJh_NAuiaCRu4gid!VXe#hT%C!)^|BUK3Cwm6?G7)c#X~wC+uK;dRj*0S1OS+Z(GH
zUo(T+_YBa25mwJAFvxE;X5?mv^sV)mbCeFkPW1$ECyuO6_1RS%D4lA@dQg)c)Pt4<
z<#Tlg1|3kk=4W6q1o7n=7`#BV3<E<Vh*oA`D1^$Ff%ug7xb;EJS#Vb!+?o}Fwq}K(
ztyv)k25@Uu4U%7R_qZod_^!e^gB#N01$VjSC*S!Vz<C4S#Rhe|Cx`sd;N;+ev`uBF
zgL>VQm;6}3X~6?AAKdAdpZ-UHF$B`{7DexQd$2Pw@PV>9M&~;W*7>$Y?|eJJOb5ps
zqMwZ3`7U8+U~mFw1oRI04sZ|J3cUmFfz*S>*8vydnEp<XQOp*-2hP9?X)1!^9$yc<
zfCJuCMDK++VDE)Ph0%NA5Mf9!yaBTpF2D`%h3^3O!Z$t_2IbN_pvs7WfdQ6F;k|Hq
zNNW%jkf^P}WfZgq`B7SfuSKvm2AhuvAh!n%54^0#Yz!XQzJCEn8OeQo!p*+z3zu_9
zG7gOqfHE32>ITCI07|1y8``K-M{CrnFfh1)YAPWH22W5UPKALX07NS>FvNps@)~v4
zq&Mm)8xdFmZNNcC1j-N%xD(I@oFb$FcLl8h_i(ymJBL0abR^*B^g;*^++h0&X|OSZ
z8fnl58z+dZ&MF9RumyB*NH9Ws{yL})H5X6|O`XvXL}516BEStbjGliQL^Y_*1!~*C
zhExl{O)<vL(-(Gd2&;ky!a)5O<Wd#Av)>14eW7>ur@&iZpk@}x3Rv^W1JZm#@9)1L
zvcJCsq8+`zzX00$0y!67f1d%|`oiez3qaaf=zV>tFnV8K0Nlpn6yQSX>x1eMXkR}9
z+Si{BDz`_cE=H#=&>K*rQx^=-$p}H(PF;+4ZAQB`qg|W9-nAK>U}O+t7@c4QO<0aj
zFpf?zf*SGo`W&MZjCdy)L7k4#cF$<LXSCfj*xNm$Lj$8j1EWI&1GK7fw2B<9B1fyp
m!CFPOH&!#YH&!#XH&!#ZH&(N>H&(N@H&(N4Z>(k)t^oi`BD6sO

delta 5989
zcmZoTVApWKZUYYs<Fv`VEb^Q-Jm;f9SYxv(i!&qR`pJd{#v27fm?m-XFizXd%kh(+
z>3{u1Mhlkz%?IQsGFoh|k?4@LJRruv&}DrNtP`Z00Sp)!c)&CR10w?ig9H-;gCr9J
zgA@}3gESKZgA5Y`gY0BO1NF%%Mhi@j2s1F096gI+0vD1ArVI=WW(*7r<_ruB77Ppw
zmJ=DZH>VgYF!6<mFfcehgV{e>$S7#@6H}Xc%M~OTMV2ZsN-S4!U=$H<5ri0K0;V(=
zlo^yJ8^1^p2D$RZpa1{=Hy;t$0dnd~k;%(mXesD2FfhQynHU%tUS4NlU}*lqR3{J^
z7?9yG`NIqG`hey)JQ@DTDw#nlXEQJ`@b6;=Yv<p`Y{OMz6%ZDlQ3_Mo>(1CE+%d)W
z#lQdmkF~IZD2C=E0?wVsJ8$&%-uU<bzvc<cWA%Gpy8i$FKd5&vNI`hU1O^6%-l-WN
zq0Xrn{{8>|Vsgn#5oL!`fq;PUj2SS)n~w+_YX#|mIN$KV>lxc~br?6XNp~LF(J0Bl
zaJJ#FvI2vO0)u`^YMFjfVqQvq?(~H-II<*jQYx$zR7-Uf@`_RuQ$S3G<P0kX)uic)
znH(~k1wWo-oZi>UA;2g$y<d`3e!83~qrh~#SVn>Azc?9%rWefSP?)}8HisRf%=G)S
zISd(HrVGyDP_O4;U|<kp;9+P52R#GB4<-<wogp5|hsg6Xq@nP+8FHa~P%;o=5M?Na
z^5wwh2{Tkd`4V8h07E^LpUns|pM{|X!q;L@U<L_rGW0+M82G>%gcv46`O;uMAH$64
zALnp*PM>GS$jw%ipPX7;Jbi;Hhtl+wxf~YtDhvz)3=9m60t^gNP+FdWfq_YhfdND_
z3NkRLfcV-B44||M;#-0EN(>A>AexDRAq7OMGcXi^^b0aDl!N$63=9*Y{Ap1BIw*fL
zlz)POfuWvBfq?;(1VIMhfl7!mGBAMn8jK7KOqvV~rXX6Cfx#In?g8Q}F))OKXeI^*
z50Jq^3=FJH3=E7S3=9TPIvh%8K<RBzIuN8@7@U2L!5X}v5@k@j1xg=-((E9IX)!Q>
zqLfKvx}62%?#;2^I~k`t_%TXym84db=oJ?vmgh~6UdXX>^1h!*oGH8v3<?Yk3<}e8
z7jY;vW>25Eh(npPg_nV01z2?NA`W@Rlhf}m;!tP2Hu>N$bxs{V1_lF=+~kkH<QdOR
z7W}Qw83Pw{{4LM;ZgS#pb;fU#6Mu_OUhrFh@!#Z)zttJprpqqjQ0MI7gE&uNy6+MW
zc}B(Qxl1_I87(IV{!wRip1kmnxZquouNfE^*r3THaPr4L;*2*ZfBY@32y&`00|NsK
z1H_b9XlnB(2mTQk{00>@f|^h{+3~Nqs30g-7#J8}qM(eiYI>p&qp+YRR0>qkfb{50
zp7>YXQk9W`fs=uO!2u-1z`!tvkAYza$mgIE70D4cXu3PVx-HOjhwvkGgHkZe3qEMN
zpG-FVCoUKT6$KS&AnU(OZu}=Mn7|0}HmYbUR4qsy2!qv5KJZU~_X{Tj!v!V=21Sso
zrz<Y!kY+u?!@w|ay5n*VWmX;m28Pn@jv|cWjBPrMZ8}VCI?Qc4ENwchZ8~giI_%qY
zI225TJ+PMCMT|_7m%XrIJUaRD3v0&C$?`8VVMQUR8~~TSIEz9~cu_dLcLv9d%|ahf
z42hC0a@dw^ETAML$iM(9(Lg1cGN{B-WneIbikpG>N(>CHAeyq0480&z1`AMLl3AdZ
zWRZ}PEP|JT0aQ0DOb3@_+aV>{5pYTNffu<X+XF7i6i`aCJK&P+3A`kG11`zFO#j%!
zAwK!TZvoB#)Y6O}QktoQOEW{PrI|gbG_$<PfLgRfz|3J_V8B<t#bPbr(y^9rxf~1(
z6S0?X4B!$9y?jd`vV4mH>qal%B#12Ec3>^vPGBwHAfo8y8(0)vzMa4<-)11nw+sBx
z@-3Kgvf*`^&3td<Sf(4WGlrv<KXn8eUXvYfpPnwGz?e2!>r=z@yrUcf)8EA~8cd%j
z$tf`1ZZ=2K^ex#O0-%;x0d<>PVrWe+5qOge)WQ*BKs31uPzxpt98E4^%qAD8zF=Tr
zfVA<1rvIPAVU42!ri!Bhri|7A(?M&1DWf&OG|(Dg%4iKRWd;V62ADDf1Ec|_$iM(<
zc!3&R4?*o5Wd;UmXz`>ADwebu7_30F8Uq8U;RRCX3*sv?FvNgp%8D&#a4|(x156uI
z;WCOcFsMNt3T}{T!Wv|`jMHoQ7%kBnWNFj?@iB%?-up9|a|5(2Q-ZY03Ls_K1!${G
z2~w7wgOp{rL1o!=oy8m+j7s1p*=0~cHoXQS0BVnY2A5*L;iVY!^uQ7hbw+MbgG^sl
ziGcy!B8Rm{c0wCZu;!N<2LprY<c*JnEw`c-S`YXjNdja7sBI22;Ru=u(cnVs0-9(l
zxOfD`B&gd5v#l6hJc62l$StoA(BctflL%7F>m8bz6Tvq9f{MZ#db7dBqbMk?AT|FM
zaxgHgffSFR<O6a9toauJF5p0oLS#q$fEJG+M@S+$!U1Y9O!pd)Zd*{J5Lx#IXz>Wr
z4eIc~0xJMbHwPC3gTUmAPlZL}pfWITNN_PQh(a7(1eJod19hhtmUD;;R-iQxp~AIL
z)zG}o01*ZipqvI=3=9vL7#NhN%P!}TXBFUuHx4rd7#MmdCq56}=D?^R!nkF+q7I{4
zpbV(}3+dT*9&i5fzf=R%1qXHLU@gAgpn!aBYxs?SpNr`Yu&A5m=hBZmK`Ep+^hW0o
zuvq8e)&nKtl{dC8bYSFW-+teSV>;vZb1{rjjEwEm=Xx<7pZ>v&k;Rme57OOZQe|M!
z1Vt+!1A`tYPsuVcxPWMB28IX_t;oQT0hQ0)E@;l!%*@z6eIh@jGHVPs1B1i#y;h9M
zjJu~lv|?0eJTck#u{z_N>4w&f>Wl{_&wZ@UcxHMdi1T3jMQcX!=?APC1sGp|*y@ZQ
zK$Q4&0UJgE#vjuaZ5Y)V|4jD;QNq(5dpXn@wWm+)<q)5~0i?imx^Ez(I-~RShrJx)
z(`*?97+I#z1&Jh1H|*mOpB?}bS~5M+mQkIFhi7`1Eu$JE!*tsqMs>y`({I``sx!t+
z?*;L4rU%+Ficfd2V-#Qnv(*`MrWf{efT)FbjOwg+xEL53AkFw1UIqq>$%)U~CtXn(
zjVDkv4Dxu|rZbwOhDMGWjVVxZIC#rG#+vrpYR2~3YNqzuYUcLZYL@oeYS#AJYPRjQ
L)$Gk369qT`Qf(=d

diff --git a/LibC/unistd.cpp b/LibC/unistd.cpp
index 6efa2da1b2..81570ece70 100644
--- a/LibC/unistd.cpp
+++ b/LibC/unistd.cpp
@@ -35,5 +35,10 @@ int close(int fd)
     return Syscall::invoke(Syscall::PosixClose, fd);
 }
 
+pid_t waitpid(pid_t waitee)
+{
+    return Syscall::invoke(Syscall::PosixWaitpid, waitee);
+}
+
 }
 
diff --git a/LibC/unistd.h b/LibC/unistd.h
index 2395eadf13..078a90fe0e 100644
--- a/LibC/unistd.h
+++ b/LibC/unistd.h
@@ -10,6 +10,7 @@ pid_t getpid();
 int open(const char* path);
 ssize_t read(int fd, void* buf, size_t count);
 int close(int fd);
+pid_t waitpid(pid_t);
 
 }
 
diff --git a/Userland/sh.cpp b/Userland/sh.cpp
index 6ec7a5e42a..68d4cc24b3 100644
--- a/Userland/sh.cpp
+++ b/Userland/sh.cpp
@@ -18,7 +18,9 @@ static int runcmd(char* cmd)
     int ret = spawn(buf);
     if (ret == -1) {
         printf("spawn failed: %s\n", cmd);
+        return 1;
     }
+    waitpid(ret);
     return 0;
 }