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Tag Archives: Linux
REXX Lost and Found
A little REXX widget I wrote about 10 years ago, that I found back on an old disk:
#!/usr/bin/rexx -- -- A Generalized Rexx Filter that can be used in a pipe -- -- Usage: rexx filter.rex builtin-or-external-function-name(arg1, arg2, ...) -- or: rexx filter.rex < inputfile -- or: rexx filter.rex (boolean expression) -- -- Note 1: -- -- rexx (to invoke filter.rex) may or may not be required to get -- the redirection and piping working, dependent on the operating -- system and the REXX implementation and/or installation setup. -- -- External functions can have a simple structure, for instance: -- -- rexx filter.rex "cut.rex(!line,10:5)" or filter.rex "cut(!line,10:5)" -- -- parse arg line,poslen -- parse var poslen pos ':' length . -- /* possibly more logic, but return value should be a (modified) -- line or a boolean if the function is called as an expression */ -- return delstr(line,pos,length) -- -- Argument(s)/Option(s) or even all of the filter have to be quoted generally. -- On Windows: It's best to use '"' for all of the filtere and "'" for arguments. -- On *n?x: It's best to use "'" for all of the filter and '"' for arguments. -- On *n?x: Redirection (< and > or >> ) doesn't seem to work all of the time. -- -- Pipe variables: -- -- The input line from the pipe is represented by '!line'. -- The running line count is represented by '!count' -- The total nr of lines is respresented by '!lines' -- Using '!lines' in the filter implies buffering the input stream before -- any output is passed on to the next pipe stage. -- -- Example 1: rexx filter.rex changestr(needle,!line,newneedle) -- -- Example 2: rexx filter.rex strip(!line,'L','>') -- -- Example 3: rexx filter.rex < somefile.txt - just echoes the input -- -- Example 4: rexx filter.rex (pos('>',!line)>0) - a boolean expression -- -- Example 5: rexx filter.rex "(!count>10)" - skips first 10 lines of input -- -- Example 6: rexx filter.rex "(!count>!lines-10)" - shows last 10 lines of input -- -- rexx filter.rex <filter.rex | , -- rexx filter.rex (pos('-',!line)=1) | , -- rexx filter.rex strip(!line,'L','-') -- -- will first read and echo filter.rex, -- then output only input lines that start with '-', -- then strip leading comment identifier '--'. -- -- No copyright, no license, no guarantees, use at your own risk. -- -- And you just read the result of the pipe above. -- parse source . . me parse arg !filter do (!filter='?' | !filter='-?' | !filter='/?' | !filter='h' | !filter='-h' | !filter='/h' | !filter='--help') pipe = 'rexx "'me'"<"'me'" | rexx "'me'" (pos(''-'',!line)=1) | rexx "'me'" strip(!line,''L'',''-'')' pipe exit end !filter = strip(strip(strip(!filter,'B',' '),'B',"'"),'B','"') -- strip spaces and quotes do until (lines()>0) -- a buffered stage can delay the input stream nop end !buffered = (pos('!lines',!filter)>0) if (!buffered) then do -- buffer input stream on standard queue do !lines=1 by 1 while (lines()>0) queue linein() end !lines = queued() !queued = !lines if (!queued>0) then do -- prefetch the 1st line queue parse pull !line end end else do !queued = lines() if (!queued>0) then do -- prefetch the 1st line from stdin !line = linein() end) end do !count=1 by 1 while (!queued>0) if (!filter = '') then do -- no filter just echoes the input !out = !line end else do if (substr(!filter,1,1)='(') then do drop !out -- to verify !out is a var later on interpret '!test =' !filter -- apply the test if (!test) then do -- if test yields .true it goes out !out = !line end end else do -- apply the filter interpret '!out =' !filter end end if (var("!out")) then do -- only write if we have something call lineout ,!out end if (!buffered) then do -- if buffered, next line from queue !queued = queued() if (!queued>0) then do parse pull !line end end else do -- not buffered, next line from stdin !queued = lines() if (!queued>0) then do !line = linein() end end end exit
The single line comment ( “–” ) style, may limit the use of the above to ooREXX and Regina REXX.