g.message(1grass) GRASS GIS User's Manual g.message(1grass)
NAME
g.message - Prints a message, warning, progress info, or fatal error
in the GRASS way.
This module should be used in scripts for messages served to user.
KEYWORDS
general, support, scripts
SYNOPSIS
g.message
g.message --help
g.message [-wedpiv] message=string [debug=integer] [--help] [--ver-
bose] [--quiet] [--ui]
Flags:
-w
Print message as warning
-e
Print message as fatal error
-d
Print message as debug message
-p
Print message as progress info
-i
Print message in all modes except of quiet mode
Message is printed on GRASS_VERBOSE>=1
-v
Print message only in verbose mode
Message is printed only on GRASS_VERBOSE>=3
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog
Parameters:
message=string [required]
Text of the message to be printed
Message is printed on GRASS_VERBOSE>=2
debug=integer
Level to use for debug messages
Options: 0-5
Default: 1
DESCRIPTION
This program is to be used in Shell/Perl/Python scripts, so the author
does not need to use the echo program. The advantage of g.message is
that it formats messages just like other GRASS modules do and that its
functionality is influenced by the GRASS_VERBOSE and GRASS_MESSAGE_FOR-
MAT environment variables.
The program can be used for standard informative messages as well as
warnings (-w flag) and fatal errors (-e flag). For debugging purposes,
the -d flag will cause g.message to print a debugging message at the
given level.
NOTES
Messages containing "=" must use the full message= syntax so the parser
doesn’t get confused.
If you want a long message (multi-line) to be dealt with as a single
paragraph, use a single call to g.message with text split in the script
using the backslash as the last character. (In shell scripts don’t
close the "quote")
A blank line may be obtained with
g.message message=""
Redundant whitespace will be stripped away.
It’s advisable to single quote the messages that are to be printed lit-
erally. It prevents a number of characters (most notably, space and
the dollar sign ’$’) from being treated specifically by the shell.
When it is necessary to include, for example, a variable’s value as
part of the message, the double quotes may be used, which do not de-
prive the dollar sign of its special variable-expansion powers.
While it is known that the interactive Bash instances may treat the ex-
clamation mark ’!’ character specifically (making single quoting of it
necessary), it shouldn’t be the case for the non-interactive instances
of Bash. Nonetheless, to avoid context-based confusion later on you are
encouraged to single-quote messages that do not require $VARIABLE ex-
pansion.
Usage in Python scripts
GRASS Python Scripting Library defines special wrappers for g.message.
• debug() for g.message -d
• error() for g.message -e
• fatal() for g.message -e + exit()
• info() for g.message -i
• message() for g.message
• verbose() for g.message -v
• warning() for g.message -w
Note: The Python tab in the wxGUI can be used for entering the follow-
ing sample code:
import grass.script as gcore
gcore.warning("This is a warning")
is identical with
g.message -w message="This is a warning"
VERBOSITY LEVELS
Controlled by the "GRASS_VERBOSE" environment variable. Typically this
is set using the --quiet or --verbose command line options.
• 0 - only errors and warnings are printed
• 1 - progress messages are printed
• 2 - all module messages are printed
• 3 - additional verbose messages are printed
DEBUG LEVELS
Controlled by the "DEBUG" GRASS gisenv variable (set with g.gisenv).
Recommended levels:
• 1 - message is printed once or few times per module
• 3 - each row (raster) or line (vector)
• 5 - each cell (raster) or point (vector)
EXAMPLES
This basic example prints the message "hello" in the console:
g.message message="hello"
To print a message as an error message use the -e flag:
g.message -e message="my error"
To print a message highlighted as a debug message ("D0/0: debug") in
the console, use the -d flag. Optionally the debug level can be defined
(see also g.gisenv for details):
# Levels: (recommended levels)
# 0 - silence
# 1 - message is printed once or few times per module
# 3 - each row (raster) or line (vector)
# 5 - each cell (raster) or point (vector)
g.message -d message="debug" debug=0
To print a message highlighted as a warning message ("WARNING: my warn-
ing") in the console, use the -w flag:
g.message -w message="my warning"
SEE ALSO
GRASS variables and environment variables
g.gisenv, g.parser
AUTHOR
Jachym Cepicky
SOURCE CODE
Available at: g.message source code (history)
Accessed: unknown
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GRASS 7.8.7 g.message(1grass)
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