12. Permissions

Previous lecture chores:

What this code do?

   1 #include <unistd.h>
   2 #include <stdio.h>
   3 
   4 int main() {
   5   int i;
   6   pid_t p;
   7 
   8   p = fork();
   9   for(i=0; i<100; i++)
  10     printf("%d %s\n", p, p ? "parent":"child");
  11 
  12   pause();
  13 }

TODO See LecturesCMC/LinuxSoftware2017/04_Permissions and Books/LinuxIntro/06ChapterPermissions in Russian

H/W

• EJudge: NumCount 'Count numbers'

  Input text stream containing integer numbers and count them. Integer is a sequence of one or more decimal digits, probably leading by «-». All integers are separated by other (neither digit, nor '-') characters. Output the number of integers.

  Input:

  1 -2   3@@@@100==
  __-567,678
  7
  
  
  800
  90$ #-100
  %%%%

  Output:

  10

• EJudge: MatrixDisplay 'Display matrix'

  Input a stream of integers (each from 0…999 range), that is elements of N×N matrix, ordered by rows. Detect this N and output the matrix (note "%3d" format is used). Also note the task can not be reasonably solved when input is manual. Assume input is always redirected from file like task < example_file.

  Input:

  260   301   565   56
  895 361 993 627 180 423 198 117 370 810
  390
  
  885       314 708
  632 678    97   273 811
  976  44

  Output:

  260 301 565  56 895
  361 993 627 180 423
  198 117 370 810 390
  885 314 708 632 678
   97 273 811 976  44

• EJudge: TransArray 'Transpose a rectangular area'

  Input a rectangular matrix of M×N integers (0…999), line by line. Determine M and N, transpose matrix and output it line by line using «"%3d"» format.

  Input:

  918 707 260 475 180 691
  78 96 744 955 192 703
  619 848 745 920 505 474
  254 179 418 335 842 312
  150 122 577 574 85 966
  852 40 500 123 200 690
  328 542 277 583 352 412
  22 541 940 60 125 452
  132 592 315 309 420 888

  Output:

  918  78 619 254 150 852 328  22 132
  707  96 848 179 122  40 542 541 592
  260 744 745 418 577 500 277 940 315
  475 955 920 335 574 123 583  60 309
  180 192 505 842  85 200 352 125 420
  691 703 474 312 966 690 412 452 888

• EJudge: RotateFence 'Rotate a stack of arrays'

  Input a number of various integer sequences (0…999) line by line. Rotate the whole structure clockwise and output it using «"%3d"» format. Trailing spaces are ignored (you may both leave or strip them).

  Input:

  173 864 629
  283 277 563 969 907 785
  415 100 944 972 784 722 925 784
  446 494 65
  572 120 150 153
  511 204 743 199 963 334 955 663
  128 946 642 5 758 310 363

  Output:

  128 511 572 446 415 283 173
  946 204 120 494 100 277 864
  642 743 150  65 944 563 629
    5 199 153     972 969
  758 963         784 907
  310 334         722 785
  363 955         925
      663         784