How to print echo environment variables

Question

How do I print the environment variable just being set   NAME sam echo   NAME    empty   You can see here using eval it works  Is this the way   NAME sam eval  echo  NAME      gt  sam

User · Answer

On windows  you can print with this command in your CLI C  Users dir env   more You can view all environment variables set on your system with the env command  The list is long  so pipe the output through more to make it easier to read

User · Answer

This works too  with the semi-colon   NAME sam  echo  NAME

User · Answer

These need to go as different commands e g    NAME sam  echo   NAME  NAME sam  amp  amp  echo   NAME    The expansion  NAME to empty string is done by the shell earlier  before running echo  so at the time the NAME variable is passed to the echo command s environment  the expansion is already done  to null string    To get the same result in one command   NAME sam printenv NAME

User · Answer

The syntax   variable value command   is often used to set an environment variables for a specific process  However  you must understand which process gets what variable and who interprets it  As an example  using two shells   a 5   variable expansion by the current shell  a 3 bash -c  echo  a    variable expansion by the second shell  a 3 bash -c  echo  a    The result will be 5 for the first echo and 3 for the second

User · Answer

To bring the existing answers together with an important clarification   As stated  the problem with NAME sam echo   NAME  is that  NAME gets expanded by the current shell before assignment NAME sam takes effect   Solutions that preserve the original semantics  of the  ineffective  solution attempt NAME sam echo   NAME     Use either eval 1    as in the question itself   or printenv  as added by Aaron McDaid to heemayl s answer   or bash -c  from Ljm Dullaart s answer   in descending order of efficiency   NAME sam eval  echo   NAME      use  eval  only if you fully control the command string NAME sam printenv NAME NAME sam bash -c  echo   NAME     printenv is not a POSIX utility  but it is available on both Linux and macOS BSD   What this style of invocation   lt var gt   lt name gt  cmd      does is to define NAME    as an environment variable  that is only defined for the command being invoked    In other words  NAME only exists for the command being invoked  and has no effect on the current shell  if no variable named NAME existed before  there will be none after  a preexisting NAME variable remains unchanged    POSIX defines the rules for this kind of invocation in its Command Search and Execution chapter     The following solutions work very differently  from heemayl s answer    NAME sam  echo   NAME  NAME sam  amp  amp  echo   NAME    While they produce the same output  they instead define    a shell variable NAME  only  rather than an environment variable   if echo were a command that relied on environment variable NAME  it wouldn t be defined  or potentially defined differently from earlier    that lives on after the command    Note that every environment variable is also exposed as a shell variable  but the inverse is not true  shell variables are only visible to the current shell and its subshells  but not to child processes  such as external utilities and  non-sourced  scripts  unless they re marked as environment variables with export or declare -x       1  Technically  bash is in violation of POSIX here  as is zsh   Since eval is a special shell built-in  the preceding NAME sam assignment should cause the the variable  NAME to remain in scope after the command finishes  but that s not what happens  However  when you run bash in POSIX compatibility mode  it is compliant  dash and ksh are always compliant  The exact rules are complicated  and some aspects are left up to the implementations to decide  again  see Command Search and Execution  Also  the usual disclaimer applies  Use eval only on input you fully control or implicitly trust

[bash] How to print / echo environment variables?

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