[jira] Commented: (FELIX-1474) [gogo] result of commands is implicitly written to pipe

["Hiram Chirino (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FELIX-1474?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12749737#action_12749737 ] 

Hiram Chirino commented on FELIX-1474:
--------------------------------------

how about coupling the | syntax with an array like syntax to to setup the pipelines for each output type.  For example:

% bundles | grep felix |[ result: echo , out:err: wc ] 

basically that would allow you process the std out, std err, and result values of a command using 3 different commands or perhaps just 1.




 





> [gogo] result of commands is implicitly written to pipe
> -------------------------------------------------------
>
>                 Key: FELIX-1474
>                 URL: https://issues.apache.org/jira/browse/FELIX-1474
>             Project: Felix
>          Issue Type: Bug
>          Components: Gogo
>            Reporter: Derek Baum
>            Priority: Minor
>
> RFC132 commands are designed to be easy to create, allowing direct use of System.out
> void echo1(String[] args) {
>     StrinbgBuilder buf = new StringBuilder();
>     for (String arg : args) {
>         if (buf.length() > 0)
>             buf.append(' ');
>         buf.append(arg)
>     }
>     System.out.println(buf.toString());
> }
> but it also allows commands that return values:
> String echo2(String[] args) {
>     StrinbgBuilder buf = new StringBuilder();
>     for (String arg : args) {
>         if (buf.length() > 0)
>             buf.append(' ');
>         buf.append(arg)
>     }
>     return(buf.toString());
> }
> Both these command cause grep to match 'hello':
> % echo1 hello | grep hello
> % echo2 hello | grep hello
> This is expected with echo1, as it writes to System.out.
> It is more surprising that echo2 also works, as it doesn't write to System.out.
> In this case, the runtime is implicitly writing the result of 'echo2 hello' into the pipe.
> This is convenient, as it lets commands that don't write to System.out be used in pipelines.
> However, it can also get in the way.
> I have a grep command that writes to System.out and returns a boolean, depending on whether it matched:
> % bundles | grep felix | wc
> but in this case, the wc command gets the output from grep and also the result of grep (true)  which not wanted,
> so I would like some way of disabling this behaviour.

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