Re: make

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Author: Jon Kettenhofen
Date:  
To: Main PLUG discussion list
Subject: Re: make
it may come from

    find . . . | grep <some file name>


which is easier to remember than the method for incorporating the grep
verb in a find command.

On 08/25/2014 07:51 PM, Michael Havens wrote:
> I get it!
>
>     cat x | grep y

>
> is redundant. did I learn that when it wasn't redundant? if it never has
> been redundant I wonder why I thought the pipe was needed?
>
> :-)~MIKE~(-:
>
>
> On Mon, Aug 25, 2014 at 4:25 PM, Brian Cluff <
> <mailto:brian@snaptek.com>> wrote:
>
>     You'll need to add some single quotes to keep the shell from
>     interpreting your regex as shell code like this:

>
>     grep -E 'error|fail' {make,install,check}.fail

>
>     Without the single quotes you are telling the system to cat from
>     your set of files and look for lines with the word error and pipe
>     that to a program called fail.

>
>     I found that I did have to add the -E even thought the man page says
>     that in the GNU version of grep the basic and extended regular
>     expressions are the same... it appears that is not the case in practice.

>
>     Brian Cluff

>
>
>     On 08/25/2014 12:56 PM, Michael Havens wrote:

>
>         I have 3 files, make.fail, install.fail, and check.fail. I want
>         to check
>         for two words in those files: error and fail.

>
>         would this work?

>
>         cat {make,install,check}.fail | grep -i error|fail

>
>         I was told to put the 'E' option in to grep. Looking at the man
>         page it
>         seems that the E option is only useful if I were greping for
>         something
>         that begins with a '{'. AM I misreading the man page?

>
>         man quote:
>                  GNU grep -E attempts to support traditional usage by
>         assuming
>         that { is
>                  not   special  if  it  would  be  the  start  of  an
>         invalid
>         interval
>                  specification.  For example, the command grep -E '{1'
>         searches
>         for  the
>                  two-character  string  {1  instead  of  reporting a
>         syntax error
>         in the
>                  regular expression.  POSIX allows this behavior as  an
>         extension,  but
>                  portable scripts should avoid it.

>
>
>
>         :-)~MIKE~(-:

>
>
>         On Mon, Aug 25, 2014 at 12:24 PM, Michael Havens
>         < <mailto:bmike1@gmail.com>
>         <mailto:bmike1@gmail.com <mailto:bmike1@gmail.com>>> wrote:

>
>              you guys are so helpful! Thanks.

>
>              :-)~MIKE~(-:

>
>
>              On Sun, Aug 24, 2014 at 7:40 PM, Jon Kettenhofen
>         < <mailto:subs@kexsof.com>
>              <mailto:subs@kexsof.com <mailto:subs@kexsof.com>>> wrote:

>
>                  I like visible proofs, so here's a test I ran:
>                  (terminal output was as is shown)

>
>                  [jon@localhost ~]$ rm temp
>                  [jon@localhost ~]$ echo >>temp
>                  [jon@localhost ~]$ echo $?
>                  0
>                  [jon@localhost ~]$ cat temp

>
>                  [jon@localhost ~]$ echo >>temp 2>&1
>                  [jon@localhost ~]$ echo $?
>                  0
>                  [jon@localhost ~]$ cat temp

>
>
>                  [jon@localhost ~]$

>
>                  as you can see, no errors and the single ">" did not
>         erase the
>                  file when used in this manner.  So Mike's script should
>         work as
>                  intended
>                  at least if there is no stderr output.

>
>                  but suppose there was an error? (apologizing for the
>         length of ...)

>
>                  [jon@localhost ~]$ echo "echo" >test
>                  [jon@localhost ~]$ echo "ls temp2" >>test
>                  [jon@localhost ~]$ # test ls of non-existent file
>                  [jon@localhost ~]$ ls temp2
>                  ls: cannot access temp2: No such file or directory
>                  [jon@localhost ~]$ echo $?
>                  2
>                  [jon@localhost ~]$ # see, we get both an error and
>         stderr message
>                  [jon@localhost ~]$ # so
>                  [jon@localhost ~]$ mv test test.sh
>                  [jon@localhost ~]$ chgmod +x test.sh
>                  bash: chgmod: command not found...
>                  [jon@localhost ~]$ chmod +x test.sh
>                  [jon@localhost ~]$ # i'm not perfect!
>                  [jon@localhost ~]$ rm temp
>                  [jon@localhost ~]$ ./test.sh >>temp
>                  ls: cannot access temp2: No such file or directory
>                  [jon@localhost ~]$ echo $?
>                  2
>                  [jon@localhost ~]$ cat temp

>
>                  [jon@localhost ~]$ ./test.sh >>temp 2>&1
>                  [jon@localhost ~]$ echo $?
>                  2
>                  [jon@localhost ~]$ cat temp

>
>
>                  ls: cannot access temp2: No such file or directory
>                  [jon@localhost ~]$

>
>                  as you can see, Mike's script will work as he
>         apparently intended,
>                  providing he's using a modern version of bash.

>
>
>
>                  On 08/24/2014 09:56 PM, James Mcphee wrote:

>
>                      you've said make, append stdout (default file
>         descriptor 1)
>                      to file
>                      make.fail, assign stderr (default filedescriptor 2)
>         the same
>                      filedescriptor as stdout.  So...  If the intent was
>         to have
>                      both stderr
>                      and stdout append make.fail, then it is correct.

>
>
>                      On Sun, Aug 24, 2014 at 6:06 PM, Michael Havens
>                      < <mailto:bmike1@gmail.com>
>         <mailto:bmike1@gmail.com <mailto:bmike1@gmail.com>>
>                      <mailto:bmike1@gmail.com <mailto:bmike1@gmail.com>
>         <mailto:bmike1@gmail.com <mailto:bmike1@gmail.com>>>> wrote:

>
>                           what I really need to know is will this:

>
>                               make>>make.fail 2>&1

>
>                           send stderr and stdout to the file 'make.fail'
>         or did I
>                      write it
>                           incorrectly?

>
>                           :-)~MIKE~(-:

>
>
>                           On Sun, Aug 24, 2014 at 2:56 PM, Brian Cluff
>                      < <mailto:brian@snaptek.com>
>         <mailto:brian@snaptek.com <mailto:brian@snaptek.com>>
>                           <mailto:brian@snaptek.com
>         <mailto:brian@snaptek.com> <mailto:brian@snaptek.com
>         <mailto:brian@snaptek.com>>>>

>
>                      wrote:

>
>                               the > will delete any file that it points
>         at even
>                      if the command
>                               doesn't actually output anything.  It will
>         even
>                      delete the file
>                               is the command doesn't exist like if you
>         type grep
>                      as gerp
>                                >file, file will still be
>         created/overwritten.

>
>                               If you want to make sure that your command
>         doesn't
>                      overwrite any
>                               existing files you have to set the
>         noclobber option
>                      like:
>                               $ set -o noclobber

>
>                               A good trick to know:
>                               You can use the > to delete the contents
>         of a file
>                      without
>                               having to delete and recreate the file by
>         simply
>                      doing this:
>                               $ >yourfile

>
>                               Brian Cluff

>
>
>                               On 08/24/2014 02:36 PM, Michael Havens wrote:

>
>                                   I have a question about redirections:

>
>                                        make>>make.fail 2>&1

>
>                                   tells it make and then to send (>)
>         stderr (2)
>                      to stdout (1)
>                                   and also to
>                                   send stdout that way also (&1).
>         finally all of
>                      that gets
>                                   sent to a file
>                                   named make.fail (>>). Isn't '>>' actually
>                      'append' whereas
>                                   '>' would
>                                   work just as well so long as the file
>         didn't
>                      already exist?
>                                   If the file
>                                   did exist would I get an error or
>         would the
>                      file be overwritten?
>                                   :-)~MIKE~(-:

>
>
>
>
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>                      --
>                      James McPhee
>          <mailto:jmcphe@gmail.com>
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