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new example: unix-does-user-exist.forth

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crc 2019-05-14 11:11:15 +00:00
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RELEASE_NOTES.md
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@ -39,6 +39,8 @@ July - September window for this release.
- add mandelbrot.forth
- add shell.forth
- add sqlite3 wrapper
- add unix-does-user-exist.forth
- improved 99bottles.forth
- corrected an issue in mail.forth
- cleanup publish-examples.forth
- publish-examples.forth now uses `retro-document` to generate glossaries

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example/unix-does-user-exist.forth Normal file
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@ -0,0 +1,38 @@
This implements a word to determine if a user exists. This is done by
parsing the results of `finger`.
~~~
:pipe> (s-s) file:R unix:popen [ file:read-line ] [ unix:pclose ] bi ;
{{
:command 'finger_%s_2>&1 s:format ;
:parse ASCII:SPACE s:tokenize ;
:login? #0 a:th fetch 'Login: s:eq? ;
---reveal---
:user:exists? (s-f)
&Heap [ command pipe> parse login? ] v:preserve ;
}}
'crc user:exists?
'fakeuser user:exists?
'root user:exists?
~~~
A second way is to parse the `/etc/passwd` file.
~~~
{{
:setup (s-fs) FALSE swap ': s:append s:keep ;
:match? (fss-fsf) over s:begins-with? ;
:found (fs-fs) drop-pair TRUE s:empty s:keep ;
:check (fss-fs) match? [ found ] if ;
:seek (fs-fs) '/etc/passwd [ check ] file:for-each-line ;
---reveal---
:user:exists? (s-f)
&Heap [ setup seek drop ] v:preserve ;
}}
'crc user:exists?
'fakeuser user:exists?
'root user:exists?
~~~