Apparently read-line is not available yet. On sbcl:
(with-open-gzip-file (s "text.gz") (read-line s))
results in :
There is no applicable method for the generic function
#<STANDARD-GENERIC-FUNCTION STREAM-READ-LINE (1)>
when called with arguments
(#<GZIP-INPUT-STREAM {BC11CC9}>).
[Condition of type SIMPLE-ERROR]
Restarts:
0: [ABORT-REQUEST] Abort handling SLIME request.
1: [TERMINATE-THREAD] Terminate this thread (#<THREAD "repl-thread" {B1F4EA9}>)
Backtrace:
0: ((SB-PCL::FAST-METHOD NO-APPLICABLE-METHOD (T))
#<unavailable argument> #<unavailable argument>
#<STANDARD-GENERIC-FUNCTION STREAM-READ-LINE (1)>
(#<GZIP-INPUT-STREAM {BC11CC9}>))
1: ((SB-PCL::FAST-METHOD NO-APPLICABLE-METHOD (T))
#<unavailable argument> #<unavailable argument>
#<STANDARD-GENERIC-FUNCTION STREAM-READ-LINE (1)>
(#<GZIP-INPUT-STREAM {BC11CC9}>))
2: (READ-LINE #<GZIP-INPUT-STREAM {BC11CC9}> T NIL #<unused argument>)
3: (NIL)
4: (SB-INT:EVAL-IN-LEXENV (WITH-OPEN-GZIP-FILE (S "text.gz") (READ-LINE S)) #<NULL-LEXENV>)
I hope at some point I'll figure out how to provide stream-read-line (but not today, I am fairly new at actually using CL)