[GRASS-dev] [GRASS GIS] #2639: grass command should read commands from stdin as an interpreter would do

[GRASS GIS]

#2639: grass command should read commands from stdin as an interpreter would do
--------------------------------------------------------------------------------------+
 Reporter:  wenzeslaus                                                                |       Owner:  grass-dev@…              
     Type:  enhancement                                                               |      Status:  new                      
 Priority:  normal                                                                    |   Milestone:  7.1.0                    
Component:  Startup                                                                   |     Version:  unspecified              
 Keywords:  interface, CLI, script, batch job, GRASS_BATCH_JOB, init, standard input  |    Platform:  All                      
      Cpu:  Unspecified                                                               |  
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 GRASS GIS works as something between set of command line tools (e.g. GDAL,
 or POSIX utilities) and an interpreter with unique commands or syntax
 (Python, R). However, GRASS GIS does not behave as the former because the
 tools are not available in standard command line (system environment).
 Unfortunately, `grass` (`grass7`) command does not behave as an
 interpreter neither because it does not allow scripts to be executed in
 the same way as with the standard interpreters.

 Standard interpreters allow to provide commands/script as standard input:

 {{{
 $ python <<EOF
 > a = 5
 > print(a)
 > EOF
 5
 }}}

 {{{
 $ R --vanilla --silent <<EOF
 a = 5
 print(a)
 EOF
 > a = 5
 > print(a)
 [1] 5
 >
 }}}

 {{{
 $ bash <<EOF
 A=5
 echo \$A
 EOF
 }}}

 {{{
 $ sqlite3 <<EOF
 SELECT 1;
 EOF

 1
 }}}

 `grass` actually allows to do the same and the commands are executed.

 {{{
 $ grass -text -c /grassdata/nc_spm/practice3/ <<EOF
 g.list rast -p
 EOF
 }}}

 However, the behavior is significantly different from standard
 interpreters: screen is reset and a lot of other text is printed. To see
 what is happening, we can redirect stdout to a file.

 {{{
 $ grass -text -c /grassdata/nc_spm/practice3/ > output.txt <<EOF
 g.list rast -p
 EOF
 }}}

 The following standard error output is shown in the command line:

 {{{
 Cleaning up temporary files...
 Creating new GRASS GIS location/mapset...

           __________  ___   __________    _______________
          / ____/ __ \/   | / ___/ ___/   / ____/  _/ ___/
         / / __/ /_/ / /| | \__ \\_  \   / / __ / / \__ \
        / /_/ / _, _/ ___ |___/ /__/ /  / /_/ // / ___/ /
        \____/_/ |_/_/  |_/____/____/   \____/___//____/

 Welcome to GRASS GIS 7.1.svn (r64884)
 GRASS GIS homepage:                      http://grass.osgeo.org
 This version running through:            Bash Shell (/bin/bash)
 Help is available with the command:      g.manual -i
 See the licence terms with:              g.version -c
 Start the GUI with:                      g.gui wxpython
 When ready to quit enter:                exit

 Cleaning up temporary files...
 Done.

 Goodbye from GRASS GIS
 }}}

 Output file as displayed by `less output.txt` contains characters to
 reset/clean the terminal:

 {{{
 ESC[HESC[2J----------------------------------------------

 raster files available in mapset <PERMANENT>:
 aspect                    elevation_shade           lsat7_2002_70
 basin_50K                 facility                  lsat7_2002_80
 ...
 elev_state_500m           lsat7_2002_61             zipcodes_dbl
 elevation                 lsat7_2002_62

 ESC[HESC[2J
 }}}

 The question is also if there should be the screen cleaning/reset at all;
 neither Python nor R are using it:

 {{{
 $
 $ python
 Python 2.7.6 (default, Mar 22 2014, 22:59:56)
 [GCC 4.8.2] on linux2
 Type "help", "copyright", "credits" or "license" for more information.
 >>> exit()
 $
 }}}

 {{{
 $
 $ R

 R version 3.0.2 (2013-09-25) -- "Frisbee Sailing"
 Copyright (C) 2013 The R Foundation for Statistical Computing
 Platform: x86_64-pc-linux-gnu (64-bit)

 R is free software and comes with ABSOLUTELY NO WARRANTY.
 You are welcome to redistribute it under certain conditions.
 Type 'license()' or 'licence()' for distribution details.

   Natural language support but running in an English locale

 R is a collaborative project with many contributors.
 Type 'contributors()' for more information and
 'citation()' on how to cite R or R packages in publications.

 Type 'demo()' for some demos, 'help()' for on-line help, or
 'help.start()' for an HTML browser interface to help.
 Type 'q()' to quit R.

 > q()
 Save workspace image? [y/n/c]: n
 $
 }}}

 Regarding the welcome text (version, copyright, help, etc.) `python` and
 `sqlite3` distinguish between interactive invocation (`python`) and input
 from script or stdin (`python script.py`, `python <<EOF`) and don't show
 anything in later case.

 With `R` we need to use `--silent` to suppress the welcome text but it
 actually checks the type of interaction too and requires additional
 parameters (e.g. `--vanilla`) when running in non-interactive mode. It
 must be noted that R has `Rscript` which is dedicated to running R scripts
 but it does not support input from stdin.

 === What should be enhanced ===

 When standard (non-interactive) input is provided or a specific command
 line option set, `grass` command should not perform cleaning of the
 terminal and perhaps should be less verbose.

 This is of course partially overlapping with #2579 but it is an important
 use case which we should take care of explicitly. Perhaps this behavior
 can be activated when the `grass batch` / `grass exec` / `grass run` /
 `grass script` / `grass --batch` syntax is used.

-- 
Ticket URL: <http://trac.osgeo.org/grass/ticket/2639>
GRASS GIS <http://grass.osgeo.org>