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IDProjectCategoryView StatusDate SubmittedLast Update
00012551003.1(2016/18)/Issue7+TC2System Interfacespublic2019-06-08 12:312024-06-11 09:08
Reporterstephane Assigned To 
PrioritynormalSeverityObjectionTypeEnhancement Request
Status ClosedResolutionAccepted As Marked 
NameStephane Chazelas
Organization
User Reference
Sectionglob(), EXAMPLES section
Page Number1111 (in the 2018 edition)
Line Number37598
Interp Status---
Final Accepted Text0001255:0004487
Summary0001255: improper shell code in glob() example
DescriptionEven though it is not the main point of that example, the POSIX specification should avoid showing examples of bad shell coding practice.

Here, that:

   ls -l *.c

Should be:

   ls -ld -- *.c

As the obvious intention of that code is to list the attributes of the non-hidden files whose name ends in .c.

The example does say "approximately" which leaves it unclear in which way it differs. One of the differences in functionality is when the glob doesn't match any file, which could be easily addressed by adding the GLOB_NOCHECK flag.
Desired ActionReplace all occurrences of "ls -l *.c" with "ls -ld -- *.c", "ls -l *.c *.h" with "ls -ld -- *.c *.h"

Change the first example to:

  globbuf.gl_offs = 3;
  if (glob("*.c", GLOB_DOOFFS|GLOB_NOCHECK, NULL, &globbuf)) abort();

  globbuf.gl_pathv[0] = "ls";
  globbuf.gl_pathv[1] = "-ld";
  globbuf.gl_pathv[2] = "--";


The second to:

  globbuf.gl_offs = 3;
  if (glob("*.c", GLOB_DOOFFS|GLOB_NOCHECK, NULL, &globbuf) ||
      glob("*.h", GLOB_DOOFFS|GLOB_NOCHECK|GLOB_APPEND, NULL, &globbuf)) abort();


Possibly clarify in which way it differs or does not differ from the sh equivalent. Like state that it should result in the execution of ls with the same list of arguments.
Tagstc3-2008

Activities

geoffclare

2019-07-18 12:08

manager   bugnote:0004486

If we add GLOB_NOCHECK as suggested to reduce the difference between using glob()+execvp() and executing "ls -ld -- *.c" in the shell, then we should add GLOB_ERR as well.

I don't like the half-way-house error checking that just calls abort(). We should either not add error checking (do we do it in any other example application code?) or add "proper" error checking.

geoffclare

2019-07-18 16:18

manager   bugnote:0004487

Last edited: 2019-07-18 16:18

 On page 1111 line 37598,37600 section glob(), change:
    ls -l *.c
to:
    ls -ld -- *.c

On page 1111 line 37609 section glob(), change:
    ls -l *.c *.h
to:
    ls -ld -- *.c *.h

On page 1111 line 37601 section glob(), change:
    
    The application could obtain approximately the same result using the sequence:

to:
    
    The application could obtain the same result (except for error handling, omitted here for simplicity) using the sequence:

Change the first example (lines 37603-37606) to:
  globbuf.gl_offs = 3;
  glob("*.c", GLOB_DOOFFS|GLOB_NOCHECK|GLOB_ERR, NULL, &globbuf);
  globbuf.gl_pathv[0] = "ls";
  globbuf.gl_pathv[1] = "-ld";
  globbuf.gl_pathv[2] = "--"; // to establish the initial arguments that
                              // sh -c "ls -ld --" would produce for both examples
The second (lines 37610-37614) to:
    
  could be simulated using GLOB_APPEND as follows:
  globbuf.gl_offs = 3;
  glob("*.c", GLOB_DOOFFS|GLOB_NOCHECK|GLOB_ERR, NULL, &globbuf);
  glob("*.h", GLOB_DOOFFS|GLOB_NOCHECK|GLOB_ERR|GLOB_APPEND, NULL, &globbuf);
  ...


Issue History

Date Modified Username Field Change
2019-06-08 12:31 stephane New Issue
2019-06-08 12:31 stephane Name => Stephane Chazelas
2019-06-08 12:31 stephane Section => glob(), EXAMPLES section
2019-06-08 12:31 stephane Page Number => 1111 (in the 2018 edition)
2019-06-08 12:31 stephane Line Number => 37598
2019-07-18 12:08 geoffclare Note Added: 0004486
2019-07-18 16:18 geoffclare Note Added: 0004487
2019-07-18 16:18 geoffclare Note Edited: 0004487
2019-07-18 16:19 geoffclare Interp Status => ---
2019-07-18 16:19 geoffclare Final Accepted Text => 0000529:0001255
2019-07-18 16:19 geoffclare Status New => Resolved
2019-07-18 16:19 geoffclare Resolution Open => Accepted As Marked
2019-07-18 16:20 geoffclare Final Accepted Text 0000529:0001255 => 0001255:0004487
2019-07-18 16:20 geoffclare Tag Attached: tc3-2008
2019-11-19 16:28 geoffclare Status Resolved => Applied
2024-06-11 09:08 agadmin Status Applied => Closed