make

[Jon Kettenhofen]

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

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

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


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

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


ls: cannot access temp2: No such file or directory
[jon at 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 <bmike1 at gmail.com
> <mailto:bmike1 at 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 <brian at snaptek.com
>     <mailto:brian at 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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> jmcphe at gmail.com <mailto:jmcphe at gmail.com>
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