On Thursday, 28 January 2021 at 17:18:46 UTC, Ali Çehreli wrote:
On 1/28/21 2:16 AM, Anthony wrote:
> auto p = pipeProcess("ls");
> auto q = pipeProcess("cat", stdin = p.stdout); //it would be
good to do
That would work if `cat` received the *contents* of the files
(and with a "-" command line switch). Since `ls` produces file
names, you would have to make the complete `cat` command line
from `ls`'s output.
> Do I need to manually extract the output from
pipes.stdin.readln
Seems to be so for the `ls | cat` case. But the following `find
| grep` example shows how two ends of pipes can be connected:
import std.stdio;
import std.process;
import std.range;
// BONUS: Enable one of the following lines to enjoy an issue.
// version = bonus_bug;
// version = bonus_bug_but_this_works;
void main() {
// Writes to 'a':
auto a = pipe();
auto lsPid = spawnProcess([ "find", "."], stdin, a.writeEnd);
scope (exit) wait(lsPid);
// Reads from 'a', writes to 'b':
auto b = pipe();
auto catPid = spawnProcess([ "grep", "-e", `\.d$` ],
a.readEnd, b.writeEnd);
scope (exit) wait(catPid);
version (bonus_bug) {
// Fails with the following error.
//
// "/usr/include/dmd/phobos/std/typecons.d(6540): Error:
// `"Attempted to access an uninitialized payload."`"
writefln!"Some of the D source files under the current
directory:\n%-( %s\n%)"(
b.readEnd.byLine);
} else version (bonus_bug_but_this_works) {
// Note .take at the end:
writefln!"Some of the D source files under the current
directory:\n%-( %s\n%)"(
b.readEnd.byLine.take(1000));
} else {
// The results are read from 'b':
writeln(b.readEnd.byLine);
}
}
I've discovered a strange issue, which can be observed by
uncommenting the 'version = bonus_bug;' line above. But comment
that one back in and uncomment the next line, now it works. (?)
Ali
Thanks Ali.
I was messing around and below seems to work well enough for me.
```
struct AccumulatorPipe {
Pid[] pids;
File stdin;
File stdout;
}
AccumulatorPipe run(string cmd) {
AccumulatorPipe acc;
auto p = P.pipeShell(cmd, P.Redirect.stdout);
acc.pids ~= p.pid;
acc.stdout = p.stdout;
return acc;
}
AccumulatorPipe pipe(AccumulatorPipe acc0, string cmd) {
AccumulatorPipe acc;
Pipe p = P.pipe();
acc.stdin = p.writeEnd;
acc.stdout = p.readEnd;
auto pid = P.spawnShell(cmd, acc0.stdout, acc.stdin);
acc.pids = acc0.pids ~ pid;
return acc;
}
void end(AccumulatorPipe acc) {
auto pids = acc.pids ~ P.spawnShell("cat", acc.stdout);
foreach (pid; pids) {
P.wait(pid);
}
}
```
So now I can do something like:
```
run("find source -name '*.d'")
.pipe("entr ./make.d tests")
.end(),
```
That would work if `cat` received the *contents* of the files
(and with a "-" command line switch)
I was actually trying to use cat to just spit out the filenames
of the directory as a test.
But I see what you mean.