Bash Echoing a echo command with a variable in bash

Question

Ok  here is one I am struggling with as we speak  Echoing a echo command with a variable   echo  creating new script file   echo     bin bash   gt   servsfile echo  read -p  Please enter a service    ser    gt  gt   servfile echo  servicetest  getsebool -a   grep   ser      gt  gt   servfile echo  if    servicetest  gt   dev null   then    gt  gt   servfile echo  echo  we are now going to work with   ser      gt  gt   servfile echo  else   gt  gt   servfile echo  exit 1   gt  gt   servfile echo  fi   gt  gt   servfile   My goal is create a script using echo commands then run it later  I just need to figure out how to echo echo read commands while maintaining my variables    edit  the variables need to transfer what s inside of them into the new file

User · Answer

echo  echo  we are now going to work with   ser      gt  gt   servfile   Escape all   within quotes with    Do this with variables like   servicetest too   echo  echo   we are now going to work with    ser       gt  gt   servfile     echo  read -p   Please enter a service     ser    gt  gt   servfile echo  if     servicetest  gt   dev null   then    gt  gt   servfile

User · Answer

The immediate problem is you have is with quoting  by using double quotes   quot     quot    your variable references are instantly expanded  which is probably not what you want  Use single quotes instead - strings inside single quotes are not expanded or interpreted in any way by the shell   If you want selective expansion inside a string - i e   expand some variable references  but not others - do use double quotes  but prefix the   of references you do not want expanded with    e g     var   However  you re better off using a single here-doc ument   which allows you to create multi-line stdin input on the spot  bracketed by two instances of a self-chosen delimiter  the opening one prefixed by  lt  lt   and the closing one on a line by itself - starting at the very first column  search for Here Documents in man bash or at http   www gnu org software bash manual html node Redirections html  If you quote the here-doc delimiter  EOF in the code below   variable references are also not expanded  As  chepner points out  you re free to choose the method of quoting in this case  enclose the delimiter in single quotes or double quotes  or even simply arbitrarily escape one character in the delimiter with    echo  quot creating new script file  quot   cat  lt  lt  EOF    gt   quot  servfile quot     bin bash read -p  quot Please enter a service   quot  ser servicetest  getsebool -a   grep   ser    if    servicetest  gt   dev null    then    echo  quot we are now going to work with   ser  quot  else   exit 1 fi EOF  As  BruceK notes  you can prefix your here-doc delimiter with -  applied to this example   lt  lt - quot EOF quot   in order to have leading tabs stripped  allowing for indentation that makes the actual content of the here-doc easier to discern  Note  however  that this only works with actual tab characters  not leading spaces  Employing this technique combined with the afterthoughts regarding the script s content below  we get  again  note that actual tab chars  must be used to lead each here-doc content line for them to get stripped   cat  lt  lt - EOF   gt   quot  servfile quot         bin bash     read -p  quot Please enter a service name   quot  ser     if    -n   getsebool -a   grep  quot   ser  quot       then        echo  quot We are now going to work with   ser   quot      else       exit 1     fi EOF  Finally  note that in bash even normal single- or double-quoted strings can span multiple lines  but you won t get the benefits of tab-stripping or line-block scoping  as everything inside the quotes becomes part of the string  Thus  note how in the following    bin bash has to follow the opening   immediately in order to become the first line of output  echo     bin bash read -p  quot Please enter a service   quot  ser servicetest   getsebool -a   grep  quot   ser  quot   if    -n  servicetest     then    echo  quot we are now going to work with   ser  quot  else   exit 1 fi   gt   quot  servfile quot    Afterthoughts regarding the contents of your script   The syntax        is preferred over       for command substitution nowadays  You should double-quote   ser  in the grep command  as the command will likely break if the value contains embedded spaces  alternatively  make sure that the valued read contains no spaces or other shell metacharacters   Use    -n  servicetest    to test whether  servicetest is empty  or perform the command substitution directly inside the conditional  -           - the preferred form in bash - protects you from breaking the conditional if the  servicetest happens to have embedded spaces  there s NEVER a need to suppress stdout output inside a conditional  whether         or            as no stdout output is passed through  thus  the  gt   dev null is redundant  that said  with a command substitution inside a conditional  stderr output IS passed through

User · Answer

You just need to use single quotes     echo   TEST  test   echo   TEST   TEST   Inside single quotes special characters are not special any more  they are just normal characters

[bash] Bash: Echoing a echo command with a variable in bash

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