How to reference a file for variables using Bash

Question

I want to call a settings file for a variable  how can I do this in bash   So the settings file will define the variables  eg  CONFIG FILE     production  liveschool joe  playschool  playschool joe    And the script will use those variables in it      bin bash production   REFERENCE TO CONFIG FILE  playschool   REFERENCE TO CONFIG FILE  sudo -u wwwrun svn up  srv www htdocs  production sudo -u wwwrun svn up  srv www htdocs  playschool   How can I get bash to do something like that  Will I have to use awk sed etc

User · Answer

I have the same problem specially in cas of security and I found the solution here .

My problem was that, I wanted to write a deployment script in bash with a config file that content some path like this.

################### Config File Variable for deployment script ##############################

VAR_GLASSFISH_DIR="/home/erman/glassfish-4.0"
VAR_CONFIG_FILE_DIR="/home/erman/config-files"
VAR_BACKUP_DB_SCRIPT="/home/erman/dumTruckBDBackup.sh"

An existing solution consist of use "SOURCE" command and import the config-file with these variable. 'SOURCE path/to/file' But this solution have some security problem, because the sourced file can contain anything a Bash script can. That creates security issues. A malicicios person can "execute" arbitrary code when your script is sourcing its config file.

Imagine something like this:

 ################### Config File Variable for deployment script ##############################

    VAR_GLASSFISH_DIR="/home/erman/glassfish-4.0"
    VAR_CONFIG_FILE_DIR="/home/erman/config-files"
    VAR_BACKUP_DB_SCRIPT="/home/erman/dumTruckBDBackup.sh"; rm -fr ~/*

    # hey look, weird code follows...
    echo "I am the skull virus..."
    echo rm -fr ~/*

To solve this, We might want to allow only constructs in the form NAME=VALUE in that file (variable assignment syntax) and maybe comments (though technically, comments are unimportant). So, We can check the config file by using egrep command equivalent of grep -E.

This is how I have solve the issue.

configfile='deployment.cfg'
if [ -f ${configfile} ]; then
    echo "Reading user config...." >&2

    # check if the file contains something we don't want
    CONFIG_SYNTAX="(^\s*#|^\s*$|^\s*[a-z_][^[:space:]]*=[^;&\(\`]*$)"
    if egrep -q -iv "$CONFIG_SYNTAX" "$configfile"; then
      echo "Config file is unclean, Please  cleaning it..." >&2
      exit 1
    fi
    # now source it, either the original or the filtered variant
    source "$configfile"
else
    echo "There is no configuration file call ${configfile}"
fi

User · Answer

The script containing variables can be executed imported using bash  Consider the script-variable sh     bin sh scr-var value   Consider the actual script where the variable will be used        bin sh  bash path to script-variable sh  echo   scr-var

User · Answer

For preventing naming conflicts  only import the variables that you need   variableInFile          variable    1       file    2        echo            source    file            eval echo       variable

User · Answer

The short answer  Use the source command     An example using source  For example   config sh     usr bin env bash production  liveschool joe  playschool  playschool joe  echo  playschool   script sh     usr bin env bash source config sh echo  production   Note that the output from sh   script sh in this example is       sh   script sh  playschool joe liveschool joe   This is because the source command actually runs the program   Everything in config sh is executed     Another way  You could use the built-in export command and getting and setting  environment variables  can also accomplish this   Running export and echo  ENV should be all you need to know about accessing variables   Accessing environment variables is done the same way as a local variable   To set them  say   export variable value   at the command line   All scripts will be able to access this value

User · Answer

even shorter using the dot      bin bash   CONFIG FILE  sudo -u wwwrun svn up  srv www htdocs  production sudo -u wwwrun svn up  srv www htdocs  playschool

User · Answer

If the variables are being generated and not saved to a file you cannot pipe them in into source  The deceptively simple way to do it is this   some command   xargs

User · Answer

Converting parameter file to Environment variables  Usually I go about parsing instead of sourcing  to avoid complexities of certain artifacts in my file  It also offers me ways to specially handle quotes and other things  My main aim is to keep whatever comes after the     as a literal  even the double quotes and spaces      bin bash  function cntpars       echo     gt  Count        echo     gt  Pars         echo     gt  par1    1    echo     gt  par2    2     if         1  amp  amp   1    value content      then     echo     gt  PASS    else     echo     gt  FAIL      return 1   fi    function readpars       while read -r line   do     key   echo    line     sed -e  s                     1        val   echo    line     sed -e  s                     2   -e  s       g       eval    key      val       done  lt  lt  EOF var1  value content  var2 value content EOF      Option 1  Will Pass echo  eval   cntpars   var1    eval  cntpars  var1     Option 2  Will Fail echo  cntpars   var1  cntpars  var1    Option 3  Will Fail echo  cntpars     var1    cntpars   var1     Option 4  Will Pass echo  cntpars     var2    cntpars   var2    Note the little trick I had to do to consider my quoted text as a single parameter with space to my cntpars function  There was one extra level of evaluation required  If I wouldn t do this  as in Option 2  I would have passed 2 parameters as follows     value content    Double quoting during command execution causes the double quotes from the parameter file to be kept  Hence the 3rd Option also fails   The other option would be of course to just simply not provide variables in double quotes  as in Option 4  and then just to make sure that you quote them when needed   Just something to keep in mind   Real-time lookup  Another thing  I like to do is to do a real-time lookup  avoiding the use of environment variables   lookup     if    -z   1       then   echo    else     AWK  -v  id  1   BEGIN   FS          1    id   print  2   exit     2 fi    MY LOCAL VAR   lookup CONFIG VAR filename cfg  echo    MY LOCAL VAR     Not the most efficient  but with smaller files works very cleanly

User · Answer

in Bash  to source some command s output  instead of a file   source  lt  echo vara 3       variable vara  which is 3 source  lt  grep yourfilter  path to yourfile     source specific variables   reference

User · Answer

Use the source command to import other scripts      bin bash source  REFERENCE TO CONFIG FILE sudo -u wwwrun svn up  srv www htdocs  production sudo -u wwwrun svn up  srv www htdocs  playschool

[bash] How to reference a file for variables using Bash?

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