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https://issues.apache.org/jira/browse/FELIX-1474?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12749837#action_12749837
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Derek Baum commented on FELIX-1474:
-----------------------------------
I was thinking of a simpler approach, that doesn't introduce new syntax:
Currently, Pipe.run() does this:
for (List<CharSequence> statement : statements)
{
result = closure.executeStatement(statement);
if (result != null && pout != null)
{
out.println(closure.session.format(result,
Converter.INSPECT));
}
}
I was thinking of adding a session variable to control this behaviour, e.g.
pipeformat = inspect
if the variable is not set, then default to the current behaviour.
if the value of pipeformat is a valid Converter format (i.e. inspect | line |
part), then print the result to the pipe using this format;
otherwise don't print the result to the pipe.
So, setting pipeformat=none would stop results being automatically written to
the pipe.
> [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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