Setting an environment variable before a command in Bash is not working for the second command in a pipe

Question

In a given shell  normally I d set a variable or variables and then run a command  Recently I learned about the concept of prepending a variable definition to a command   FOO bar somecommand someargs   This works    kind of  It doesn t work when you re changing a LC   variable  which seems to affect the command  but not its arguments  for example    a-z   char ranges  or when piping output to another command thusly   FOO bar somecommand someargs   somecommand2    somecommand2 is unaware of FOO   I can prepend somecommand2 with  FOO bar  as well  which works  but which adds unwanted duplication  and it doesn t help with arguments that are interpreted depending on the variable  for example    a-z      So  what s a good way to do this on a single line   I m thinking something on the order of   FOO bar  somecommand someargs   somecommand2     Doesn t actually work     I got lots of good answers  The goal is to keep this a one-liner  preferably without using  export   The method using a call to Bash was best overall  though the parenthetical version with  export  in it was a little more compact  The method of using redirection rather than a pipe is interesting as well

User · Answer

How about exporting the variable  but only inside the subshell     export FOO bar  amp  amp  somecommand someargs   somecommand2    Keith has a point  to unconditionally execute the commands  do this    export FOO bar  somecommand someargs   somecommand2

User · Answer

You can also use eval   FOO bar eval  somecommand someargs   somecommand2      Since this answer with eval doesn t seem to please everyone  let me clarify something  when used as written  with the single quotes  it is perfectly safe  It is good as it will not launch an external process  like the accepted answer  nor will it execute the commands in an extra subshell  like the other answer    As we get a few regular views  it s probably good to give an alternative to eval that will please everyone  and has all the benefits  and perhaps even more   of this quick eval    trick      Just use a function  Define a function with all your commands   mypipe         somecommand someargs   somecommand2     and execute it with your environment variables like this   FOO bar mypipe

User · Answer

Use env   For example  env FOO BAR command  Note that the environment variables will be restored unchanged again when command finishes executing   Just be careful about about shell substitution happening  i e  if you want to reference  FOO explicitly on the same command line  you may need to escape it so that your shell interpreter doesn t perform the substitution before it runs env     export FOO BAR   env FOO FUBAR bash -c  echo  FOO  FUBAR   echo  FOO BAR

User · Answer

FOO bar bash -c  somecommand someargs   somecommand2

User · Answer

Use a shell script      bin bash   myscript FOO bar somecommand someargs   somecommand2   gt    myscript

User · Answer

A simple approach is to make use of     For example     ENV prod  ansible-playbook -i inventories  ENV --extra-vars  env  ENV   deauthorize users yml --check

[bash] Setting an environment variable before a command in Bash is not working for the second command in a pipe

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