Bash conditionals how to and expressions if -z VAR -e VAR

Question

I guess I m not clear on how to do  and  tests  I wanted to make sure an argument existed which was working well with   -e  VAR    but it turns out that was also evaluating as true on an empty string  which I do not want   How do I  and  them together  Or is there another unary test that accomplishes what I want

User · Answer

if   -n   var  -a -e   var     then     do something     fi    nbsp

User · Answer

Simply quote your variable     -e   VAR      This evaluates to   -e      if  VAR is empty   Your version does not work because it evaluates to   -e    Now in this case  bash simply checks if the single argument  -e  is a non-empty string   From the manpage      test and   evaluate conditional expressions using a set of rules based on the number of arguments           1 argument       The expression is true if and only if the argument is not null      Also  this solution has the additional benefit of working with filenames containing spaces

User · Answer

if     -z   var     amp  amp    -e   var     then         something     fi

User · Answer

From the bash manpage         expression    - return  a status of 0 or 1 depending on the evaluation of the conditional expression expression    And  for expressions  one of the options is      expression1  amp  amp  expression2 - true if both expression1 and expression2 are true    So you can and them together as follows  -n is the opposite of -z so we can get rid of the      if    -n   var   amp  amp  -e   var       then     echo    var  is non-empty and the file exists  fi   However  I don t think it s needed in this case  -e xyzzy is true if the xyzzy file exists and can quite easily handle empty strings  If that s what you want then you don t actually need the -z non-empty check   pax gt  VAR xyzzy pax gt  if    -e  VAR      then echo yes   fi pax gt  VAR  tmp pax gt  if    -e  VAR      then echo yes   fi yes   In other words  just use   if    -e   var       then     echo    var  exists  fi

User · Answer

I found an answer now  Thanks for your suggestions   for e in     cutoff txt  do if grep -q -E  COX1 Cu-oxidase   e then     echo xyz  gt  e match txt else     echo fi  if grep -q -E  AMO   e then     echo abc  gt  e match txt else     echo fi  done   Any comments on that  It seems inefficient to grep twice  but it works

[bash] Bash conditionals: how to "and" expressions? (if [ ! -z $VAR && -e $VAR ])

Examples related to bash

Examples related to shell