aboutsummaryrefslogtreecommitdiff
path: root/nix/libutil/util.cc
blob: a4a1ddb12a02cc0aa7cac33a7c87ae67ccff8be7 (about) (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
#include "config.h"

#include "util.hh"
#include "affinity.hh"

#include <iostream>
#include <cerrno>
#include <cstdio>
#include <cstdlib>
#include <sstream>
#include <cstring>

#include <sys/wait.h>
#include <unistd.h>
#include <fcntl.h>
#include <limits.h>

#ifdef __APPLE__
#include <sys/syscall.h>
#endif


extern char * * environ;


namespace nix {


BaseError::BaseError(const FormatOrString & fs, unsigned int status)
    : status(status)
{
    err = fs.s;
}


BaseError & BaseError::addPrefix(const FormatOrString & fs)
{
    prefix_ = fs.s + prefix_;
    return *this;
}


SysError::SysError(const FormatOrString & fs)
    : Error(format("%1%: %2%") % fs.s % strerror(errno))
    , errNo(errno)
{
}


string getEnv(const string & key, const string & def)
{
    char * value = getenv(key.c_str());
    return value ? string(value) : def;
}


Path absPath(Path path, Path dir)
{
    if (path[0] != '/') {
        if (dir == "") {
#ifdef __GNU__
            /* GNU (aka. GNU/Hurd) doesn't have any limitation on path
               lengths and doesn't define `PATH_MAX'.  */
            char *buf = getcwd(NULL, 0);
            if (buf == NULL)
#else
            char buf[PATH_MAX];
            if (!getcwd(buf, sizeof(buf)))
#endif
                throw SysError("cannot get cwd");
            dir = buf;
#ifdef __GNU__
            free(buf);
#endif
        }
        path = dir + "/" + path;
    }
    return canonPath(path);
}


Path canonPath(const Path & path, bool resolveSymlinks)
{
    string s;

    if (path[0] != '/')
        throw Error(format("not an absolute path: `%1%'") % path);

    string::const_iterator i = path.begin(), end = path.end();
    string temp;

    /* Count the number of times we follow a symlink and stop at some
       arbitrary (but high) limit to prevent infinite loops. */
    unsigned int followCount = 0, maxFollow = 1024;

    while (1) {

        /* Skip slashes. */
        while (i != end && *i == '/') i++;
        if (i == end) break;

        /* Ignore `.'. */
        if (*i == '.' && (i + 1 == end || i[1] == '/'))
            i++;

        /* If `..', delete the last component. */
        else if (*i == '.' && i + 1 < end && i[1] == '.' &&
            (i + 2 == end || i[2] == '/'))
        {
            if (!s.empty()) s.erase(s.rfind('/'));
            i += 2;
        }

        /* Normal component; copy it. */
        else {
            s += '/';
            while (i != end && *i != '/') s += *i++;

            /* If s points to a symlink, resolve it and restart (since
               the symlink target might contain new symlinks). */
            if (resolveSymlinks && isLink(s)) {
                if (++followCount >= maxFollow)
                    throw Error(format("infinite symlink recursion in path `%1%'") % path);
                temp = absPath(readLink(s), dirOf(s))
                    + string(i, end);
                i = temp.begin(); /* restart */
                end = temp.end();
                s = "";
            }
        }
    }

    return s.empty() ? "/" : s;
}


Path dirOf(const Path & path)
{
    Path::size_type pos = path.rfind('/');
    if (pos == string::npos)
        throw Error(format("invalid file name `%1%'") % path);
    return pos == 0 ? "/" : Path(path, 0, pos);
}


string baseNameOf(const Path & path)
{
    Path::size_type pos = path.rfind('/');
    if (pos == string::npos)
        throw Error(format("invalid file name `%1%'") % path);
    return string(path, pos + 1);
}


bool isInDir(const Path & path, const Path & dir)
{
    return path[0] == '/'
        && string(path, 0, dir.size()) == dir
        && path.size() >= dir.size() + 2
        && path[dir.size()] == '/';
}


struct stat lstat(const Path & path)
{
    struct stat st;
    if (lstat(path.c_str(), &st))
        throw SysError(format("getting status of `%1%'") % path);
    return st;
}


bool pathExists(const Path & path)
{
    int res;
    struct stat st;
    res = lstat(path.c_str(), &st);
    if (!res) return true;
    if (errno != ENOENT && errno != ENOTDIR)
        throw SysError(format("getting status of %1%") % path);
    return false;
}


Path readLink(const Path & path)
{
    checkInterrupt();
    struct stat st = lstat(path);
    if (!S_ISLNK(st.st_mode))
        throw Error(format("`%1%' is not a symlink") % path);
    char buf[st.st_size];
    if (readlink(path.c_str(), buf, st.st_size) != st.st_size)
        throw SysError(format("reading symbolic link `%1%'") % path);
    return string(buf, st.st_size);
}


bool isLink(const Path & path)
{
    struct stat st = lstat(path);
    return S_ISLNK(st.st_mode);
}


DirEntries readDirectory(const Path & path)
{
    DirEntries entries;
    entries.reserve(64);

    AutoCloseDir dir = opendir(path.c_str());
    if (!dir) throw SysError(format("opening directory `%1%'") % path);

    struct dirent * dirent;
    while (errno = 0, dirent = readdir(dir)) { /* sic */
        checkInterrupt();
        string name = dirent->d_name;
        if (name == "." || name == "..") continue;
        entries.emplace_back(name, dirent->d_ino, dirent->d_type);
    }
    if (errno) throw SysError(format("reading directory `%1%'") % path);

    return entries;
}


unsigned char getFileType(const Path & path)
{
    struct stat st = lstat(path);
    if (S_ISDIR(st.st_mode)) return DT_DIR;
    if (S_ISLNK(st.st_mode)) return DT_LNK;
    if (S_ISREG(st.st_mode)) return DT_REG;
    return DT_UNKNOWN;
}


string readFile(int fd)
{
    struct stat st;
    if (fstat(fd, &st) == -1)
        throw SysError("statting file");

    unsigned char * buf = new unsigned char[st.st_size];
    AutoDeleteArray<unsigned char> d(buf);
    readFull(fd, buf, st.st_size);

    return string((char *) buf, st.st_size);
}


string readFile(const Path & path, bool drain)
{
    AutoCloseFD fd = open(path.c_str(), O_RDONLY);
    if (fd == -1)
        throw SysError(format("opening file `%1%'") % path);
    return drain ? drainFD(fd) : readFile(fd);
}


void writeFile(const Path & path, const string & s)
{
    AutoCloseFD fd = open(path.c_str(), O_WRONLY | O_TRUNC | O_CREAT, 0666);
    if (fd == -1)
        throw SysError(format("opening file `%1%'") % path);
    writeFull(fd, (unsigned char *) s.data(), s.size());
}


string readLine(int fd)
{
    string s;
    while (1) {
        checkInterrupt();
        char ch;
        ssize_t rd = read(fd, &ch, 1);
        if (rd == -1) {
            if (errno != EINTR)
                throw SysError("reading a line");
        } else if (rd == 0)
            throw EndOfFile("unexpected EOF reading a line");
        else {
            if (ch == '\n') return s;
            s += ch;
        }
    }
}


void writeLine(int fd, string s)
{
    s += '\n';
    writeFull(fd, (const unsigned char *) s.data(), s.size());
}


static void _deletePath(const Path & path, unsigned long long & bytesFreed)
{
    checkInterrupt();

    printMsg(lvlVomit, format("%1%") % path);

    struct stat st = lstat(path);

    if (!S_ISDIR(st.st_mode) && st.st_nlink == 1)
        bytesFreed += st.st_blocks * 512;

    if (S_ISDIR(st.st_mode)) {
        /* Make the directory writable. */
        if (!(st.st_mode & S_IWUSR)) {
            if (chmod(path.c_str(), st.st_mode | S_IWUSR) == -1)
                throw SysError(format("making `%1%' writable") % path);
        }

        for (auto & i : readDirectory(path))
            _deletePath(path + "/" + i.name, bytesFreed);
    }

    if (remove(path.c_str()) == -1)
        throw SysError(format("cannot unlink `%1%'") % path);
}


void deletePath(const Path & path)
{
    unsigned long long dummy;
    deletePath(path, dummy);
}


void deletePath(const Path & path, unsigned long long & bytesFreed)
{
    startNest(nest, lvlDebug,
        format("recursively deleting path `%1%'") % path);
    bytesFreed = 0;
    _deletePath(path, bytesFreed);
}


static Path tempName(Path tmpRoot, const Path & prefix, bool includePid,
    int & counter)
{
    tmpRoot = canonPath(tmpRoot.empty() ? getEnv("TMPDIR", "/tmp") : tmpRoot, true);
    if (includePid)
        return (format("%1%/%2%-%3%-%4%") % tmpRoot % prefix % getpid() % counter++).str();
    else
        return (format("%1%/%2%-%3%") % tmpRoot % prefix % counter++).str();
}


Path createTempDir(const Path & tmpRoot, const Path & prefix,
    bool includePid, bool useGlobalCounter, mode_t mode)
{
    static int globalCounter = 0;
    int localCounter = 0;
    int & counter(useGlobalCounter ? globalCounter : localCounter);

    while (1) {
        checkInterrupt();
        Path tmpDir = tempName(tmpRoot, prefix, includePid, counter);
        if (mkdir(tmpDir.c_str(), mode) == 0) {
            /* Explicitly set the group of the directory.  This is to
               work around around problems caused by BSD's group
               ownership semantics (directories inherit the group of
               the parent).  For instance, the group of /tmp on
               FreeBSD is "wheel", so all directories created in /tmp
               will be owned by "wheel"; but if the user is not in
               "wheel", then "tar" will fail to unpack archives that
               have the setgid bit set on directories. */
            if (chown(tmpDir.c_str(), (uid_t) -1, getegid()) != 0)
                throw SysError(format("setting group of directory `%1%'") % tmpDir);
            return tmpDir;
        }
        if (errno != EEXIST)
            throw SysError(format("creating directory `%1%'") % tmpDir);
    }
}


Paths createDirs(const Path & path)
{
    Paths created;
    if (path == "/") return created;

    struct stat st;
    if (lstat(path.c_str(), &st) == -1) {
        created = createDirs(dirOf(path));
        if (mkdir(path.c_str(), 0777) == -1 && errno != EEXIST)
            throw SysError(format("creating directory `%1%'") % path);
        st = lstat(path);
        created.push_back(path);
    }

    if (S_ISLNK(st.st_mode) && stat(path.c_str(), &st) == -1)
        throw SysError(format("statting symlink `%1%'") % path);

    if (!S_ISDIR(st.st_mode)) throw Error(format("`%1%' is not a directory") % path);

    return created;
}


void createSymlink(const Path & target, const Path & link)
{
    if (symlink(target.c_str(), link.c_str()))
        throw SysError(format("creating symlink from `%1%' to `%2%'") % link % target);
}


LogType logType = ltPretty;
Verbosity verbosity = lvlInfo;

static int nestingLevel = 0;


Nest::Nest()
{
    nest = false;
}


Nest::~Nest()
{
    close();
}


static string escVerbosity(Verbosity level)
{
    return int2String((int) level);
}


void Nest::open(Verbosity level, const FormatOrString & fs)
{
    if (level <= verbosity) {
        if (logType == ltEscapes)
            std::cerr << "\033[" << escVerbosity(level) << "p"
                      << fs.s << "\n";
        else
            printMsg_(level, fs);
        nest = true;
        nestingLevel++;
    }
}


void Nest::close()
{
    if (nest) {
        nestingLevel--;
        if (logType == ltEscapes)
            std::cerr << "\033[q";
        nest = false;
    }
}


void printMsg_(Verbosity level, const FormatOrString & fs)
{
    checkInterrupt();
    if (level > verbosity) return;
    string prefix;
    if (logType == ltPretty)
        for (int i = 0; i < nestingLevel; i++)
            prefix += "|   ";
    else if (logType == ltEscapes && level != lvlInfo)
        prefix = "\033[" + escVerbosity(level) + "s";
    string s = (format("%1%%2%\n") % prefix % fs.s).str();
    writeToStderr(s);
}


void warnOnce(bool & haveWarned, const FormatOrString & fs)
{
    if (!haveWarned) {
        printMsg(lvlError, format("warning: %1%") % fs.s);
        haveWarned = true;
    }
}


static void defaultWriteToStderr(const unsigned char * buf, size_t count)
{
    writeFull(STDERR_FILENO, buf, count);
}


void writeToStderr(const string & s)
{
    try {
        auto p = _writeToStderr;
        if (!p) p = defaultWriteToStderr;
        p((const unsigned char *) s.data(), s.size());
    } catch (SysError & e) {
        /* Ignore failing writes to stderr if we're in an exception
           handler, otherwise throw an exception.  We need to ignore
           write errors in exception handlers to ensure that cleanup
           code runs to completion if the other side of stderr has
           been closed unexpectedly. */
        if (!std::uncaught_exception()) throw;
    }
}


void (*_writeToStderr) (const unsigned char * buf, size_t count) = defaultWriteToStderr;


void readFull(int fd, unsigned char * buf, size_t count)
{
    while (count) {
        checkInterrupt();
        ssize_t res = read(fd, (char *) buf, count);
        if (res == -1) {
            if (errno == EINTR) continue;
            throw SysError("reading from file");
        }
        if (res == 0) throw EndOfFile("unexpected end-of-file");
        count -= res;
        buf += res;
    }
}


void writeFull(int fd, const unsigned char * buf, size_t count)
{
    while (count) {
        checkInterrupt();
        ssize_t res = write(fd, (char *) buf, count);
        if (res == -1) {
            if (errno == EINTR) continue;
            throw SysError("writing to file");
        }
        count -= res;
        buf += res;
    }
}


string drainFD(int fd)
{
    string result;
    unsigned char buffer[4096];
    while (1) {
        checkInterrupt();
        ssize_t rd = read(fd, buffer, sizeof buffer);
        if (rd == -1) {
            if (errno != EINTR)
                throw SysError("reading from file");
        }
        else if (rd == 0) break;
        else result.append((char *) buffer, rd);
    }
    return result;
}



//////////////////////////////////////////////////////////////////////


AutoDelete::AutoDelete(const string & p, bool recursive) : path(p)
{
    del = true;
    this->recursive = recursive;
}

AutoDelete::~AutoDelete()
{
    try {
        if (del) {
            if (recursive)
                deletePath(path);
            else {
                if (remove(path.c_str()) == -1)
                    throw SysError(format("cannot unlink `%1%'") % path);
            }
        }
    } catch (...) {
        ignoreException();
    }
}

void AutoDelete::cancel()
{
    del = false;
}



//////////////////////////////////////////////////////////////////////


AutoCloseFD::AutoCloseFD()
{
    fd = -1;
}


AutoCloseFD::AutoCloseFD(int fd)
{
    this->fd = fd;
}


AutoCloseFD::AutoCloseFD(const AutoCloseFD & fd)
{
    /* Copying an AutoCloseFD isn't allowed (who should get to close
       it?).  But as an edge case, allow copying of closed
       AutoCloseFDs.  This is necessary due to tiresome reasons
       involving copy constructor use on default object values in STL
       containers (like when you do `map[value]' where value isn't in
       the map yet). */
    this->fd = fd.fd;
    if (this->fd != -1) abort();
}


AutoCloseFD::~AutoCloseFD()
{
    try {
        close();
    } catch (...) {
        ignoreException();
    }
}


void AutoCloseFD::operator =(int fd)
{
    if (this->fd != fd) close();
    this->fd = fd;
}


AutoCloseFD::operator int() const
{
    return fd;
}


void AutoCloseFD::close()
{
    if (fd != -1) {
        if (::close(fd) == -1)
            /* This should never happen. */
            throw SysError(format("closing file descriptor %1%") % fd);
        fd = -1;
    }
}


bool AutoCloseFD::isOpen()
{
    return fd != -1;
}


/* Pass responsibility for closing this fd to the caller. */
int AutoCloseFD::borrow()
{
    int oldFD = fd;
    fd = -1;
    return oldFD;
}


void Pipe::create()
{
    int fds[2];
    if (pipe(fds) != 0) throw SysError("creating pipe");
    readSide = fds[0];
    writeSide = fds[1];
    closeOnExec(readSide);
    closeOnExec(writeSide);
}



//////////////////////////////////////////////////////////////////////


AutoCloseDir::AutoCloseDir()
{
    dir = 0;
}


AutoCloseDir::AutoCloseDir(DIR * dir)
{
    this->dir = dir;
}


AutoCloseDir::~AutoCloseDir()
{
    close();
}


void AutoCloseDir::operator =(DIR * dir)
{
    this->dir = dir;
}


AutoCloseDir::operator DIR *()
{
    return dir;
}


void AutoCloseDir::close()
{
    if (dir) {
        closedir(dir);
        dir = 0;
    }
}


//////////////////////////////////////////////////////////////////////


Pid::Pid()
    : pid(-1), separatePG(false), killSignal(SIGKILL)
{
}


Pid::Pid(pid_t pid)
    : pid(pid), separatePG(false), killSignal(SIGKILL)
{
}


Pid::~Pid()
{
    kill();
}


void Pid::operator =(pid_t pid)
{
    if (this->pid != pid) kill();
    this->pid = pid;
    killSignal = SIGKILL; // reset signal to default
}


Pid::operator pid_t()
{
    return pid;
}


void Pid::kill(bool quiet)
{
    if (pid == -1 || pid == 0) return;

    if (!quiet)
        printMsg(lvlError, format("killing process %1%") % pid);

    /* Send the requested signal to the child.  If it has its own
       process group, send the signal to every process in the child
       process group (which hopefully includes *all* its children). */
    if (::kill(separatePG ? -pid : pid, killSignal) != 0)
        printMsg(lvlError, (SysError(format("killing process %1%") % pid).msg()));

    /* Wait until the child dies, disregarding the exit status. */
    int status;
    while (waitpid(pid, &status, 0) == -1) {
        checkInterrupt();
        if (errno != EINTR) {
            printMsg(lvlError,
                (SysError(format("waiting for process %1%") % pid).msg()));
            break;
        }
    }

    pid = -1;
}


int Pid::wait(bool block)
{
    assert(pid != -1);
    while (1) {
        int status;
        int res = waitpid(pid, &status, block ? 0 : WNOHANG);
        if (res == pid) {
            pid = -1;
            return status;
        }
        if (res == 0 && !block) return -1;
        if (errno != EINTR)
            throw SysError("cannot get child exit status");
        checkInterrupt();
    }
}


void Pid::setSeparatePG(bool separatePG)
{
    this->separatePG = separatePG;
}


void Pid::setKillSignal(int signal)
{
    this->killSignal = signal;
}


void killUser(uid_t uid)
{
    debug(format("killing all processes running under uid `%1%'") % uid);

    assert(uid != 0); /* just to be safe... */

    /* The system call kill(-1, sig) sends the signal `sig' to all
       users to which the current process can send signals.  So we
       fork a process, switch to uid, and send a mass kill. */

    Pid pid = startProcess([&]() {

        if (setuid(uid) == -1)
            throw SysError("setting uid");

        while (true) {
#ifdef __APPLE__
            /* OSX's kill syscall takes a third parameter that, among
               other things, determines if kill(-1, signo) affects the
               calling process. In the OSX libc, it's set to true,
               which means "follow POSIX", which we don't want here
                 */
            if (syscall(SYS_kill, -1, SIGKILL, false) == 0) break;
#else
            if (kill(-1, SIGKILL) == 0) break;
#endif
            if (errno == ESRCH) break; /* no more processes */
            if (errno != EINTR)
                throw SysError(format("cannot kill processes for uid `%1%'") % uid);
        }

        _exit(0);
    });

    int status = pid.wait(true);
    if (status != 0)
        throw Error(format("cannot kill processes for uid `%1%': %2%") % uid % statusToString(status));

    /* !!! We should really do some check to make sure that there are
       no processes left running under `uid', but there is no portable
       way to do so (I think).  The most reliable way may be `ps -eo
       uid | grep -q $uid'. */
}


//////////////////////////////////////////////////////////////////////


pid_t startProcess(std::function<void()> fun,
    bool dieWithParent, const string & errorPrefix, bool runExitHandlers)
{
    pid_t pid = fork();
    if (pid == -1) throw SysError("unable to fork");

    if (pid == 0) {
        _writeToStderr = 0;
        try {
            restoreAffinity();
            fun();
        } catch (std::exception & e) {
            try {
                std::cerr << errorPrefix << e.what() << "\n";
            } catch (...) { }
        } catch (...) { }
        if (runExitHandlers)
            exit(1);
        else
            _exit(1);
    }

    return pid;
}


string runProgram(Path program, bool searchPath, const Strings & args)
{
    checkInterrupt();

    std::vector<const char *> cargs; /* careful with c_str()! */
    cargs.push_back(program.c_str());
    for (Strings::const_iterator i = args.begin(); i != args.end(); ++i)
        cargs.push_back(i->c_str());
    cargs.push_back(0);

    /* Create a pipe. */
    Pipe pipe;
    pipe.create();

    /* Fork. */
    Pid pid = startProcess([&]() {
        if (dup2(pipe.writeSide, STDOUT_FILENO) == -1)
            throw SysError("dupping stdout");

        if (searchPath)
            execvp(program.c_str(), (char * *) &cargs[0]);
        else
            execv(program.c_str(), (char * *) &cargs[0]);

        throw SysError(format("executing `%1%'") % program);
    });

    pipe.writeSide.close();

    string result = drainFD(pipe.readSide);

    /* Wait for the child to finish. */
    int status = pid.wait(true);
    if (!statusOk(status))
        throw ExecError(format("program `%1%' %2%")
            % program % statusToString(status));

    return result;
}


void closeMostFDs(const set<int> & exceptions)
{
    int maxFD = 0;
    maxFD = sysconf(_SC_OPEN_MAX);
    for (int fd = 0; fd < maxFD; ++fd)
        if (fd != STDIN_FILENO && fd != STDOUT_FILENO && fd != STDERR_FILENO
            && exceptions.find(fd) == exceptions.end())
            close(fd); /* ignore result */
}


void closeOnExec(int fd)
{
    int prev;
    if ((prev = fcntl(fd, F_GETFD, 0)) == -1 ||
        fcntl(fd, F_SETFD, prev | FD_CLOEXEC) == -1)
        throw SysError("setting close-on-exec flag");
}


//////////////////////////////////////////////////////////////////////


volatile sig_atomic_t _isInterrupted = 0;

void _interrupted()
{
    /* Block user interrupts while an exception is being handled.
       Throwing an exception while another exception is being handled
       kills the program! */
    if (!std::uncaught_exception()) {
        _isInterrupted = 0;
        throw Interrupted("interrupted by the user");
    }
}



//////////////////////////////////////////////////////////////////////


template<class C> C tokenizeString(const string & s, const string & separators)
{
    C result;
    string::size_type pos = s.find_first_not_of(separators, 0);
    while (pos != string::npos) {
        string::size_type end = s.find_first_of(separators, pos + 1);
        if (end == string::npos) end = s.size();
        string token(s, pos, end - pos);
        result.insert(result.end(), token);
        pos = s.find_first_not_of(separators, end);
    }
    return result;
}

template Strings tokenizeString(const string & s, const string & separators);
template StringSet tokenizeString(const string & s, const string & separators);
template vector<string> tokenizeString(const string & s, const string & separators);


string concatStringsSep(const string & sep, const Strings & ss)
{
    string s;
    foreach (Strings::const_iterator, i, ss) {
        if (s.size() != 0) s += sep;
        s += *i;
    }
    return s;
}


string concatStringsSep(const string & sep, const StringSet & ss)
{
    string s;
    foreach (StringSet::const_iterator, i, ss) {
        if (s.size() != 0) s += sep;
        s += *i;
    }
    return s;
}


string chomp(const string & s)
{
    size_t i = s.find_last_not_of(" \n\r\t");
    return i == string::npos ? "" : string(s, 0, i + 1);
}


string statusToString(int status)
{
    if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
        if (WIFEXITED(status))
            return (format("failed with exit code %1%") % WEXITSTATUS(status)).str();
        else if (WIFSIGNALED(status)) {
            int sig = WTERMSIG(status);
#if HAVE_STRSIGNAL
            const char * description = strsignal(sig);
            return (format("failed due to signal %1% (%2%)") % sig % description).str();
#else
            return (format("failed due to signal %1%") % sig).str();
#endif
        }
        else
            return "died abnormally";
    } else return "succeeded";
}


bool statusOk(int status)
{
    return WIFEXITED(status) && WEXITSTATUS(status) == 0;
}


bool hasSuffix(const string & s, const string & suffix)
{
    return s.size() >= suffix.size() && string(s, s.size() - suffix.size()) == suffix;
}


void expect(std::istream & str, const string & s)
{
    char s2[s.size()];
    str.read(s2, s.size());
    if (string(s2, s.size()) != s)
        throw FormatError(format("expected string `%1%'") % s);
}


string parseString(std::istream & str)
{
    string res;
    expect(str, "\"");
    int c;
    while ((c = str.get()) != '"')
        if (c == '\\') {
            c = str.get();
            if (c == 'n') res += '\n';
            else if (c == 'r') res += '\r';
            else if (c == 't') res += '\t';
            else res += c;
        }
        else res += c;
    return res;
}


bool endOfList(std::istream & str)
{
    if (str.peek() == ',') {
        str.get();
        return false;
    }
    if (str.peek() == ']') {
        str.get();
        return true;
    }
    return false;
}


string decodeOctalEscaped(const string & s)
{
    string r;
    for (string::const_iterator i = s.begin(); i != s.end(); ) {
        if (*i != '\\') { r += *i++; continue; }
        unsigned char c = 0;
        ++i;
        while (i != s.end() && *i >= '0' && *i < '8')
            c = c * 8 + (*i++ - '0');
        r += c;
    }
    return r;
}


void ignoreException()
{
    try {
        throw;
    } catch (std::exception & e) {
        printMsg(lvlError, format("error (ignored): %1%") % e.what());
    }
}


}