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Variable indirection

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Top Forums Shell Programming and Scripting Variable indirection
# 8  
Old 05-26-2012
Quote:
Originally Posted by bakunin
It is indeed possible, but you have to be aware about the different number of times the line gets evaluated with and without eval.

If you use eval var='$(...)' to execute it you should probably print it with the same number of evals. But to be honest i have a feeling that your whole script is not planned very well because the structures you use are looking wrong anyway. I may be wrong, but if you post your whole script and tell us what you want to achieve we could find a better way to do it than with such crooked measures.

I hope this helps.

bakunin
My script is not doing more than the example I gave.

Code:
#!/bin/bash
#
My_CMD1="some texte and parameter $PARAM1 $PARAM2  without quote"
# Want to print to screen
# for debugging
echo "The command is : $MY_CMD1"
# now execute it
$MY_CMD1
# OK no problem with this case
#
#Trying this one
#
PARAM1="No"
PARAM2="Not installed"
PARAM3="FreeNX"
PARAM4="My_freenx_Directory"
PARAM5="/tmp/install_test/freenx.log"
#
zypper info -r $PARAM4 > $PARAM5
#
# We try to verify if the log file contains the information
# that prove that the software is not installed
# 4 parameters are nedeed
#
# For good understanding I replace all quote (simple or double) with this : %
# and each time the single quote ( ' )  is necessary I put it in the right place
# So the next line is not the real one
#
MY_CMD2=%CNT=$( grep -c  -e  %some_text1 $PARAM1%  -e  %some_text2 '$PARAM2'%  -e  %some_text3-1 $PARAM3-1 some_text3-2 '$PARAM4'%  -e %some_text4% $PARAM4%    $PARAM_5 ) %
#
# If the software is not installed, CNT = 4
#
# now try to print the command to screen ( very important for debugging )
echo "The command is : $MY_CMD2"
# now execute it
$MY_CMD2
# Problem with this case
#

I get this working with 2 conditions :
1°)I must separate the variable content (because of ( " ) and ( ' ) ) for printing or for execute
2°)I use eval for execute --> eval $MY_CMD2

Code:
#!/bin/bash
#
My_CMD1="some texte and parameter $PARAM1 $PARAM2  without quote"
# Want to print to screen
# for debugging
echo "The command is : $MY_CMD1"
# now execute it
$MY_CMD1
# OK no problem with this case
#
#Trying this one
#
PARAM1="No"
PARAM2="Not installed"
PARAM3="FreeNX"
PARAM4="My_freenx_Directory"
PARAM5="/tmp/install_test/freenx.log"
#
zypper info -r $PARAM4 > $PARAM5
#
# We try to verify if the log file contains the information
# that prove that the software is not installed
# 4 parameters are nedeed
#
# For good understanding I replace all quote (simple or double) with this : %
# and each time the single quote ( ' )  is necessary I put it in the right place
# So the next line is not the real one
#
# MY_CMD3 is use for echoing to the screen and have to put some more single and double quote.
#
MY_CMD3=%CNT=$( grep -c  -e  %some_text1 $PARAM1%  -e  %some_text2  '$PARAM2'%  -e  %some_text3-1 $PARAM3-1 some_text3-2 '$PARAM4'%  -e  %some_text4% $PARAM4%    $PARAM_5 ) %
#
# MY_CMD4 use some different single and double quote ,where single quote are mandatory.
#
$MY_CMD4=%CNT=$( grep -c  -e  %some_text1 $PARAM1%  -e  %some_text2  %%'$PARAM2'%%  -e  %some_text3-1 $PARAM3-1 some_text3-2  %%'$PARAM4'%%  -e  %some_text4% $PARAM4%    $PARAM_5 ) %
 #
# now try to print the command to screen ( very important for debugging )
echo "The command is : $MY_CMD3"
# now execute it
eval $MYCMD4
# No Problem with this case
#

CMD_3 -->
Code:
CMD='CNT=$(  grep -c -e  "Non-option program arguments: '"'$PACKAGE_1'"'"  -e  "Checking whether to refresh metadata for '$REPO_1'" -e  "Selecting '"'FreeNX-0.7.3-22.1.x86_64'"' from repository '"'$REPO_1'"' for installation."    '$LOG_FILE_1' ) '

CMD_4 -->
Code:
CMD='CNT=$(  grep -c -e  "Non-option program arguments: '"'"'$PACKAGE_1'"'"'"  -e  "Checking whether to refresh metadata for $REPO_1" -e  "Selecting '"'"'FreeNX-0.7.3-22.1.x86_64'"'"' from repository '"'"'$REPO_1'"'"' for installation."  $LOG_FILE_1 ) '

Last edited by Scrutinizer; 05-27-2012 at 02:06 AM.. Reason: code tags instead of quote tags
# 9  
Old 06-04-2012
Quote:
Originally Posted by Scrutinizer
If you try double quotes instead of single quotes, I think it becomes a bit more straight forward, you should then escape the double quotes with a backslash, plus the $-signs that you wish to protect from evaluation during assignment:
Code:
CMD="CNT=\$( grep -c -e \"Non-option program arguments: '$PACKAGE_1'\" -e \"Checking whether to refresh metadata for $REPO_1\" -e \"Selecting '$PACKAGE_1-3.5.0-7.x86_64' from repository '$REPO_1' for installation.\" \"$LOG_FILE_1\" )"

Code:
eval CMD$

Works great if quoted correctly as you show me.

The thread is closed.

Thank you every body for your help and for your patience.
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