What does export do in shell programming

Question

As far as I can tell  variable assignment is the same whether it is or is not preceded by  export   What s it for

User · Answer

it makes the assignment visible to subprocesses    foo bar   bash -c  echo  foo     export foo   bash -c  echo  foo  bar

User · Answer

Well  it generally depends on the shell  For bash  it marks the variable as  quot exportable quot  meaning that it will show up in the environment for any child processes you run  Non-exported variables are only visible from the current process  the shell   From the bash man page   export  -fn   name  word       export -p The supplied names are marked for automatic export to the environment of subsequently executed commands  If the -f option is given  the names refer to functions   If no names are given  or if the -p option is supplied  a list of all names that are exported in this shell is printed  The -n option causes the export property  to  be removed  from  each  name  If  a variable name is followed by  word  the value of the variable is set to word  export returns an exit status of 0 unless an invalid option is encountered  one of the names is not a valid shell variable name  or -f is supplied with a name that is not a function   You can also set variables as exportable with the typeset command and automatically mark all future variable creations or modifications as such  with set -a

User · Answer

Exported variables such as  HOME and  PATH are available to  inherited by  other programs run by the shell that exports them  and the programs run by those other programs  and so on  as environment variables   Regular  non-exported  variables are not available to other programs     env   grep   variable                                       No environment variable called variable   variable Hello                    Create local  non-exported  variable with value   env   grep   variable                                       Still no environment variable called variable   export variable                   Mark variable for export to child processes   env   grep   variable   variable Hello     export other variable Goodbye     create and initialize exported variable   env   grep   other variable   other variable Goodbye     For more information  see the entry for the export builtin in the GNU Bash manual  and also the sections on command execution environment and environment   Note that non-exported variables will be available to subshells run via         and similar notations because those subshells are direct clones of the main shell     othervar present    echo  othervar  echo  variable  variable elephant  echo  variable  present Hello elephant   echo  variable Hello     The subshell can change its own copy of any variable  exported or not  and may affect the values seen by the processes it runs  but the subshell s changes cannot affect the variable in the parent shell  of course   Some information about subshells can be found under command grouping and command execution environment in the Bash manual

[bash] What does "export" do in shell programming?

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