How to assign the output of a Bash command to a variable

Question

I have a problem putting the content of pwd command into a shell variable that I ll use later    Here is my shell code  the loop doesn t stop       bin bash pwd   pwd  until    pwd             do         echo  pwd         ls  amp  amp  cd     amp  amp  ls           pwd   pwd       done   Could you spot my mistake  please

User · Answer

In this specific case  note that bash has a variable called PWD that contains the current directory   PWD is equivalent to  pwd    So do other shells  this is a standard feature   So you can write your script like this      bin bash until     PWD           do   echo   PWD    ls  amp  amp  cd     amp  amp  ls  done   Note the use of double quotes around the variable references  They are necessary if the variable  here  the current directory  contains whitespace or wildcards         because the shell splits the result of variable expansions into words and performs globbing on these words  Always double-quote variable expansions   foo  and command substitutions    foo    unless you specifically know you have not to    In the general case  as other answers have mentioned already    You can t use whitespace around the equal sign in an assignment  var value  not var   value The   means    take the value of this variable     so you don t use it when assigning  var value  not  var value

User · Answer

In shell you assign to a variable without the dollar-sign   TEST  pwd  echo  TEST   that s better  and can be nested  but is not as portable as the backtics   TEST   pwd  echo  TEST   Always remember  the dollar-sign is only used when reading a variable

User · Answer

You can also do way more complex commands  just to round out the examples above  So  say I want to get the number of processes running on the system and store it in the   NUM PROCS  variable   All you have to so is generate the command pipeline and stuff it s output  the process count  into the variable   It looks something like this   NUM PROCS   ps -e   sed 1d   wc -l    I hope that helps add some handy information to this discussion

User · Answer

Try   pwd  pwd    or  pwd   pwd       Notice no spaces after the equals sign    Also as Mr  Weiss points out  you don t assign to  pwd  you assign to pwd

User · Answer

Here s your script     DIR   pwd  echo  DIR while     DIR            do     cd        DIR   pwd      echo  DIR done   Note the spaces  use of quotes  and   signs

[bash] How to assign the output of a Bash command to a variable?

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