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Full Discussion: Note: environment variables within awk
Top Forums Shell Programming and Scripting Note: environment variables within awk Post 303030789 by MadeInGermany on Friday 15th of February 2019 01:18:35 PM
Old 02-15-2019
The DEBUG=$DEBUG ensures that DEBUG exists in the environment for the awk.
But it's pure overhead if it was already in the shell's environment.
You can achieve the same with an exported variable (exported = placed in the shell's environment)
Code:
export DEBUG
test "$1" = "-v" && DEBUG=1 || DEBUG=0
mysql -e 'SHOW SLAVE STATUS \G' | mysql_slave_check

Because DEBUG is in the shell's environment, all the run commands inherit it.

The use of ENVIRON[ ] in an awk script is interesting. Thanks for sharing!
It is not used often. Reason: when awk is run from the shell there is easy passing of variables.
The Posix style:
Code:
test "$1" = "-v" && DEBUG=1 || DEBUG=0
mysql -e 'SHOW SLAVE STATUS \G' | awk -v DEBUG=$DEBUG -f mysql_slave_check

Or the (bit dirty) Unix awk style
Code:
test "$1" = "-v" && DEBUG=1 || DEBUG=0
mysql -e 'SHOW SLAVE STATUS \G' | awk -f mysql_slave_check DEBUG=$DEBUG

Either invocation sets the DEBUG variable in awk, so there is no need for pulling it from ENVIRON[ ]
These 2 Users Gave Thanks to MadeInGermany For This Post:
Neo stomp
 

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LEARN ABOUT LINUX

envsubst

ENVSUBST(1)								GNU							       ENVSUBST(1)

NAME

       envsubst - substitutes environment variables in shell format strings

SYNOPSIS

       envsubst [OPTION] [SHELL-FORMAT]

DESCRIPTION

       Substitutes the values of environment variables.

   Operation mode:
       -v, --variables
	      output the variables occurring in SHELL-FORMAT

   Informative output:
       -h, --help
	      display this help and exit

       -V, --version
	      output version information and exit

       In  normal  operation  mode, standard input is copied to standard output, with references to environment variables of the form $VARIABLE or
       ${VARIABLE} being replaced with the corresponding values.  If a SHELL-FORMAT is given, only those environment variables that are referenced
       in SHELL-FORMAT are substituted; otherwise all environment variables references occurring in standard input are substituted.

       When --variables is used, standard input is ignored, and the output consists of the environment variables that are referenced in SHELL-FOR-
       MAT, one per line.

AUTHOR

       Written by Bruno Haible.

REPORTING BUGS

       Report bugs to <bug-gnu-gettext@gnu.org>.

COPYRIGHT

       Copyright (C) 2003-2007 Free Software Foundation, Inc.  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
       This is free software: you are free to change and redistribute it.  There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

       The full documentation for envsubst is maintained as a Texinfo manual.  If the info and envsubst programs are properly  installed  at  your
       site, the command

	      info envsubst

       should give you access to the complete manual.

GNU gettext-runtime 0.18.1					     June 2010							       ENVSUBST(1)
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