Can a shell script set environment variables of the calling shell

Question

I m trying to write a shell script that  when run  will set some environment variables that will stay set in the caller s shell   setenv FOO foo   in csh tcsh  or  export FOO foo   in sh bash only set it during the script s execution   I already know that   source myscript   will run the commands of the script rather than launching a new shell  and that can result in setting the  caller s  environment   But here s the rub   I want this script to be callable from either bash or csh   In other words  I want users of either shell to be able to run my script and have their shell s environment changed   So  source  won t work for me  since a user running csh can t source a bash script  and a user running bash can t source a csh script   Is there any reasonable solution that doesn t involve having to write and maintain TWO versions on the script

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I created a solution using pipes  eval and signal   parent         if   -z   G EVAL FD     then             die 1  Rode primeiro parent setup no processo pai      fi     if     ppid            then                      else             kill -SIGUSR1                echo      gt  amp  G EVAL FD     fi   parent setup         G EVAL FD 99     tempfile   mktemp -u      mkfifo   tempfile      eval  exec  G EVAL FD lt  gt   tempfile       rm -f   tempfile      trap  read CMD  lt  amp  G EVAL FD  eval     CMD    USR1   parent setup  on parent shell context   A 1    echo  A   prints nothing   parent A 1    echo  A   prints 1   It might work with any command

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In my  bash profile I have      No Proxy function noproxy        usr local sbin noproxy   turn off proxy server     unset http proxy HTTP PROXY https proxy HTTPs PROXY       Proxy function setproxy       sh  usr local sbin proxyon   turn on proxy server      http proxy http   127 0 0 1 8118      HTTP PROXY  http proxy     https proxy  http proxy     HTTPS PROXY  https proxy     export http proxy https proxy HTTP PROXY HTTPS PROXY     So when I want to disable the proxy   the function s  run in the login shell and sets the variables as expected and wanted

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Your shell process has a copy of the parent s environment and no access to the parent process s environment whatsoever  When your shell process terminates any changes you ve made to its environment are lost  Sourcing a script file is the most commonly used method for configuring a shell environment  you may just want to bite the bullet and maintain one for each of the two flavors of shell

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Use the  dot space script  calling syntax  For example  here s how to do it using the full path to a script      path to set env vars sh   And here s how to do it if you re in the same directory as the script     set env vars sh   These execute the script under the current shell instead of loading another one  which is what would happen if you did   set env vars sh   Because it runs in the same shell  the environmental variables you set will be available when it exits    This is the same thing as calling source set env vars sh  but it s shorter to type and might work in some places where source doesn t

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Add the -l flag in top of your bash script i e      usr bin env bash -l       export NAME1  VALUE1  export NAME2  VALUE2    The values with NAME1 and NAME2 will now have been exported to your current environment  however these changes are not permanent  If you want them to be permanent you need to add them to your  bashrc file or other init file    From the man pages   -l Make bash act as if it had been invoked as a login shell  see INVOCATION below

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Your shell process has a copy of the parent s environment and no access to the parent process s environment whatsoever  When your shell process terminates any changes you ve made to its environment are lost  Sourcing a script file is the most commonly used method for configuring a shell environment  you may just want to bite the bullet and maintain one for each of the two flavors of shell

User · Answer

Your shell process has a copy of the parent s environment and no access to the parent process s environment whatsoever  When your shell process terminates any changes you ve made to its environment are lost  Sourcing a script file is the most commonly used method for configuring a shell environment  you may just want to bite the bullet and maintain one for each of the two flavors of shell

User · Answer

You should use modules  see http   modules sourceforge net   EDIT  The modules package has not been updated since 2012 but still works ok for the basics  All the new features  bells and whistles happen in lmod this day  which I like it more   https   www tacc utexas edu research-development tacc-projects lmod

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It s  kind of  possible through using gdb and setenv 3   although I have a hard time recommending actually doing this   Additionally  i e  the most recent ubuntu won t actually let you do this without telling the kernel to be more permissive about ptrace  and the same may go for other distros as well      cat setfoo     bin bash  gdb  proc   PPID  exe   PPID   lt  lt END  gt  dev null call setenv  foo    bar   0  END   echo  foo      setfoo   echo  foo bar

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Another option is to use  Environment Modules   http   modules sourceforge net    This unfortunately introduces a third language into the mix  You define the environment with the language of Tcl  but there are a few handy commands for typical modifications  prepend vs  append vs set   You will also need to have environment modules installed  You can then use module load  XXX  to name the environment you want  The module command is basically a fancy alias for the eval mechanism described above by Thomas Kammeyer  The main advantage here is that you can maintain the environment in one language and rely on  Environment Modules  to translate it to sh  ksh  bash  csh  tcsh  zsh  python          etc

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You can invoke another one Bash with the different bash profile   Also  you can create special bash profile for using in multi-bashprofile environment    Remember that you can use functions inside of bashprofile  and that functions will be avialable globally  for example   function user   export USER NAME  1    can set variable in runtime  for example  user olegchir  amp  amp  env   grep olegchir

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You should use modules  see http   modules sourceforge net   EDIT  The modules package has not been updated since 2012 but still works ok for the basics  All the new features  bells and whistles happen in lmod this day  which I like it more   https   www tacc utexas edu research-development tacc-projects lmod

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You re not going to be able to modify the caller s shell because it s in a different process context   When child processes inherit your shell s variables  they re inheriting copies themselves   One thing you can do is to write a script that emits the correct commands for tcsh or sh based how it s invoked   If you re script is  setit  then do   ln -s setit setit-sh   and  ln -s setit setit-csh   Now either directly or in an alias  you do this from sh  eval  setit-sh    or this from csh  eval  setit-csh    setit uses  0 to determine its output style   This is reminescent of how people use to get the TERM environment variable set   The advantage here is that setit is just written in whichever shell you like as in      bin bash arg0  0 arg0   arg0      for nv in      NAME1 VALUE1      NAME2 VALUE2 do    if   x arg0   xsetit-sh    then       echo  export   nv        elif   x arg0   xsetit-csh    then       echo  setenv    nv          nv             fi done   with the symbolic links given above  and the eval of the backquoted expression  this has the desired result   To simplify invocation for csh  tcsh  or similar shells   alias dosetit  eval  setit-csh     or for sh  bash  and the like   alias dosetit  eval  setit-sh     One nice thing about this is that you only have to maintain the list in one place  In theory you could even stick the list in a file and put cat nvpairfilename between  in  and  do    This is pretty much how login shell terminal settings used to be done   a script would output statments to be executed in the login shell   An alias would generally be used to make invocation simple  as in  tset vt100    As mentioned in another answer  there is also similar functionality in the INN UseNet news server

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Other than writings conditionals depending on what  SHELL  TERM is set to  no   What s wrong with using Perl   It s pretty ubiquitous  I can t think of a single UNIX variant that doesn t have it   and it ll spare you the trouble

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This works  mdash  it isn t what I d use  but it  works    Let s create a script teredo to set the environment variable TEREDO WORMS      bin ksh export TEREDO WORMS ukelele exec  SHELL -i   It will be interpreted by the Korn shell  exports the environment variable  and then replaces itself with a new interactive shell   Before running this script  we have SHELL set in the environment to the C shell  and the environment variable TEREDO WORMS is not set     env   grep SHELL SHELL  bin csh   env   grep TEREDO     When the script is run  you are in a new shell  another interactive C shell  but the environment variable is set     teredo   env   grep TEREDO TEREDO WORMS ukelele     When you exit from this shell  the original shell takes over     exit   env   grep TEREDO     The environment variable is not set in the original shell s environment   If you use exec teredo to run the command  then the original interactive shell is replaced by the Korn shell that sets the environment  and then that in turn is replaced by a new interactive C shell     exec teredo   env   grep TEREDO TEREDO WORMS ukelele     If you type exit  or Control-D   then your shell exits  probably logging you out of that window  or taking you back to the previous level of shell from where the experiments started   The same mechanism works for Bash or Korn shell   You may find that the prompt after the exit commands appears in funny places     Note the discussion in the comments   This is not a solution I would recommend  but it does achieve the stated purpose of a single script to set the environment that works with all shells  that accept the -i option to make an interactive shell    You could also add      after the option to relay any other arguments  which might then make the shell usable as a general  set environment and execute command  tool   You might want to omit the -i if there are other arguments  leading to      bin ksh export TEREDO WORMS ukelele exec  SHELL     - -i      The     - -i    bit means  if the argument list contains at least one argument  use the original argument list  otherwise  substitute -i for the non-existent arguments

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You re not going to be able to modify the caller s shell because it s in a different process context   When child processes inherit your shell s variables  they re inheriting copies themselves   One thing you can do is to write a script that emits the correct commands for tcsh or sh based how it s invoked   If you re script is  setit  then do   ln -s setit setit-sh   and  ln -s setit setit-csh   Now either directly or in an alias  you do this from sh  eval  setit-sh    or this from csh  eval  setit-csh    setit uses  0 to determine its output style   This is reminescent of how people use to get the TERM environment variable set   The advantage here is that setit is just written in whichever shell you like as in      bin bash arg0  0 arg0   arg0      for nv in      NAME1 VALUE1      NAME2 VALUE2 do    if   x arg0   xsetit-sh    then       echo  export   nv        elif   x arg0   xsetit-csh    then       echo  setenv    nv          nv             fi done   with the symbolic links given above  and the eval of the backquoted expression  this has the desired result   To simplify invocation for csh  tcsh  or similar shells   alias dosetit  eval  setit-csh     or for sh  bash  and the like   alias dosetit  eval  setit-sh     One nice thing about this is that you only have to maintain the list in one place  In theory you could even stick the list in a file and put cat nvpairfilename between  in  and  do    This is pretty much how login shell terminal settings used to be done   a script would output statments to be executed in the login shell   An alias would generally be used to make invocation simple  as in  tset vt100    As mentioned in another answer  there is also similar functionality in the INN UseNet news server

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It s not what I would call outstanding  but this also works if you need to call the script from the shell anyway  It s not a good solution  but for a single static environment variable  it works well enough    1   Create a script with a condition that exits either 0  Successful  or 1  Not successful   if     foo     True      then     exit 0 else     exit 1   2   Create an alias that is dependent on the exit code   alias  myscript sh  amp  amp  export MyVariable    You call the alias  which calls the script  which evaluates the condition  which is required to exit zero via the   amp  amp   in order to set the environment variable in the parent shell    This is flotsam  but it can be useful in a pinch

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Other than writings conditionals depending on what  SHELL  TERM is set to  no   What s wrong with using Perl   It s pretty ubiquitous  I can t think of a single UNIX variant that doesn t have it   and it ll spare you the trouble

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You can instruct the child process to print its environment variables  by calling  env    then loop over the printed environment variables in the parent process and call  export  on those variables   The following code is based on Capturing output of find   -print0 into a bash array  If the parent shell is the bash  you can use  while IFS  read -r -d    0  line  do     export   line  done  lt   lt  bash -s  lt  lt  lt   export VARNAME something  env -0   echo  VARNAME   If the parent shell is the dash  then read does not provide the -d flag and the code gets more complicated  TMPDIR   mktemp -d  mkfifo  TMPDIR fifo  bash -s  lt  lt   EOF      export VARNAME something     while IFS  read -r -d    0  line  do         echo   printf   q    line       done  lt   lt  env -0  EOF    gt   TMPDIR fifo  amp  while read -r line  do export    eval echo  line    done  lt   TMPDIR fifo rm -r  TMPDIR echo  VARNAME

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It s  kind of  possible through using gdb and setenv 3   although I have a hard time recommending actually doing this   Additionally  i e  the most recent ubuntu won t actually let you do this without telling the kernel to be more permissive about ptrace  and the same may go for other distros as well      cat setfoo     bin bash  gdb  proc   PPID  exe   PPID   lt  lt END  gt  dev null call setenv  foo    bar   0  END   echo  foo      setfoo   echo  foo bar

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Use the  dot space script  calling syntax  For example  here s how to do it using the full path to a script      path to set env vars sh   And here s how to do it if you re in the same directory as the script     set env vars sh   These execute the script under the current shell instead of loading another one  which is what would happen if you did   set env vars sh   Because it runs in the same shell  the environmental variables you set will be available when it exits    This is the same thing as calling source set env vars sh  but it s shorter to type and might work in some places where source doesn t

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Another workaround that I don t see mentioned is to write the variable value to a file   I ran into a very similar issue where I wanted to be able to run the last set test  instead of all my tests    My first plan was to write one command for setting the env variable TESTCASE  and then have another command that would use this to run the test   Needless to say that I had the same exact issue as you did   But then I came up with this simple hack   First command   testset        bin bash  if      -eq 1   then   echo  1  gt     TESTCASE   echo  TESTCASE has been set to   1  else   echo  Come again   fi   Second command  testrun        bin bash  TESTCASE   cat    TESTCASE  drush test-run  TESTCASE

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I did this many years ago  If I rememeber correctly  I included an alias in each of  bashrc and  cshrc  with parameters  aliasing the respective forms of setting the environment to a common form   Then the script that you will source in any of the two shells has a command with that last form  that is suitable aliased in each shell   If I find the concrete aliases  I will post them

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I did this many years ago  If I rememeber correctly  I included an alias in each of  bashrc and  cshrc  with parameters  aliasing the respective forms of setting the environment to a common form   Then the script that you will source in any of the two shells has a command with that last form  that is suitable aliased in each shell   If I find the concrete aliases  I will post them

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Under OS X bash you can do the following   Create the bash script file to unset the variable     bin bash unset http proxy   Make the file executable  sudo chmod 744 unsetvar   Create alias  alias unsetvar  source  your path to the script unsetvar    It should be ready to use so long you have the folder containing your script file appended to the path

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Another option is to use  Environment Modules   http   modules sourceforge net    This unfortunately introduces a third language into the mix  You define the environment with the language of Tcl  but there are a few handy commands for typical modifications  prepend vs  append vs set   You will also need to have environment modules installed  You can then use module load  XXX  to name the environment you want  The module command is basically a fancy alias for the eval mechanism described above by Thomas Kammeyer  The main advantage here is that you can maintain the environment in one language and rely on  Environment Modules  to translate it to sh  ksh  bash  csh  tcsh  zsh  python          etc

User · Answer

It s not what I would call outstanding  but this also works if you need to call the script from the shell anyway  It s not a good solution  but for a single static environment variable  it works well enough    1   Create a script with a condition that exits either 0  Successful  or 1  Not successful   if     foo     True      then     exit 0 else     exit 1   2   Create an alias that is dependent on the exit code   alias  myscript sh  amp  amp  export MyVariable    You call the alias  which calls the script  which evaluates the condition  which is required to exit zero via the   amp  amp   in order to set the environment variable in the parent shell    This is flotsam  but it can be useful in a pinch

User · Answer

Another workaround that I don t see mentioned is to write the variable value to a file   I ran into a very similar issue where I wanted to be able to run the last set test  instead of all my tests    My first plan was to write one command for setting the env variable TESTCASE  and then have another command that would use this to run the test   Needless to say that I had the same exact issue as you did   But then I came up with this simple hack   First command   testset        bin bash  if      -eq 1   then   echo  1  gt     TESTCASE   echo  TESTCASE has been set to   1  else   echo  Come again   fi   Second command  testrun        bin bash  TESTCASE   cat    TESTCASE  drush test-run  TESTCASE

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Technically  that is correct -- only  eval  doesn t fork another shell   However  from the point of view of the application you re trying to run in the modified environment  the difference is nil  the child inherits the environment of its parent  so the  modified  environment is conveyed to all descending processes   Ipso facto  the changed environment variable  sticks  -- as long as you are running under the parent program shell   If it is absolutely necessary for the environment variable to remain after the parent  Perl or shell  has exited  it is necessary for the parent shell to do the heavy lifting   One method I ve seen in the documentation is for the current script to spawn an executable file with the necessary  export  language  and then trick the parent shell into executing it -- always being cognizant of the fact that you need to preface the command with  source  if you re trying to leave a non-volatile version of the modified environment behind   A Kluge at best   The second method is to modify the script that initiates the shell environment   bashrc or whatever  to contain the modified parameter   This can be dangerous -- if you hose up the initialization script it may make your shell unavailable the next time it tries to launch   There are plenty of tools for modifying the current shell  by affixing the necessary tweaks to the  launcher  you effectively push those changes forward as well  Generally not a good idea  if you only need the environment changes for a particular application suite  you ll have to go back and return the shell launch script to its pristine state  using vi or whatever  afterwards   In short  there are no good  and easy  methods   Presumably this was made difficult to ensure the security of the system was not irrevocably compromised

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The short answer is no  you cannot alter the environment of the parent process  but it seems like what you want is an environment with custom environment variables and the shell that the user has chosen   So why not simply something like     usr bin env bash FOO foo  SHELL   Then when you are done with the environment  just exit

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I created a solution using pipes  eval and signal   parent         if   -z   G EVAL FD     then             die 1  Rode primeiro parent setup no processo pai      fi     if     ppid            then                      else             kill -SIGUSR1                echo      gt  amp  G EVAL FD     fi   parent setup         G EVAL FD 99     tempfile   mktemp -u      mkfifo   tempfile      eval  exec  G EVAL FD lt  gt   tempfile       rm -f   tempfile      trap  read CMD  lt  amp  G EVAL FD  eval     CMD    USR1   parent setup  on parent shell context   A 1    echo  A   prints nothing   parent A 1    echo  A   prints 1   It might work with any command

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The short answer is no  you cannot alter the environment of the parent process  but it seems like what you want is an environment with custom environment variables and the shell that the user has chosen   So why not simply something like     usr bin env bash FOO foo  SHELL   Then when you are done with the environment  just exit

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This works  mdash  it isn t what I d use  but it  works    Let s create a script teredo to set the environment variable TEREDO WORMS      bin ksh export TEREDO WORMS ukelele exec  SHELL -i   It will be interpreted by the Korn shell  exports the environment variable  and then replaces itself with a new interactive shell   Before running this script  we have SHELL set in the environment to the C shell  and the environment variable TEREDO WORMS is not set     env   grep SHELL SHELL  bin csh   env   grep TEREDO     When the script is run  you are in a new shell  another interactive C shell  but the environment variable is set     teredo   env   grep TEREDO TEREDO WORMS ukelele     When you exit from this shell  the original shell takes over     exit   env   grep TEREDO     The environment variable is not set in the original shell s environment   If you use exec teredo to run the command  then the original interactive shell is replaced by the Korn shell that sets the environment  and then that in turn is replaced by a new interactive C shell     exec teredo   env   grep TEREDO TEREDO WORMS ukelele     If you type exit  or Control-D   then your shell exits  probably logging you out of that window  or taking you back to the previous level of shell from where the experiments started   The same mechanism works for Bash or Korn shell   You may find that the prompt after the exit commands appears in funny places     Note the discussion in the comments   This is not a solution I would recommend  but it does achieve the stated purpose of a single script to set the environment that works with all shells  that accept the -i option to make an interactive shell    You could also add      after the option to relay any other arguments  which might then make the shell usable as a general  set environment and execute command  tool   You might want to omit the -i if there are other arguments  leading to      bin ksh export TEREDO WORMS ukelele exec  SHELL     - -i      The     - -i    bit means  if the argument list contains at least one argument  use the original argument list  otherwise  substitute -i for the non-existent arguments

User · Answer

You should use modules  see http   modules sourceforge net   EDIT  The modules package has not been updated since 2012 but still works ok for the basics  All the new features  bells and whistles happen in lmod this day  which I like it more   https   www tacc utexas edu research-development tacc-projects lmod

User · Answer

Other than writings conditionals depending on what  SHELL  TERM is set to  no   What s wrong with using Perl   It s pretty ubiquitous  I can t think of a single UNIX variant that doesn t have it   and it ll spare you the trouble

User · Answer

You could always use aliases  alias your env  source   scripts your env sh

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This works  mdash  it isn t what I d use  but it  works    Let s create a script teredo to set the environment variable TEREDO WORMS      bin ksh export TEREDO WORMS ukelele exec  SHELL -i   It will be interpreted by the Korn shell  exports the environment variable  and then replaces itself with a new interactive shell   Before running this script  we have SHELL set in the environment to the C shell  and the environment variable TEREDO WORMS is not set     env   grep SHELL SHELL  bin csh   env   grep TEREDO     When the script is run  you are in a new shell  another interactive C shell  but the environment variable is set     teredo   env   grep TEREDO TEREDO WORMS ukelele     When you exit from this shell  the original shell takes over     exit   env   grep TEREDO     The environment variable is not set in the original shell s environment   If you use exec teredo to run the command  then the original interactive shell is replaced by the Korn shell that sets the environment  and then that in turn is replaced by a new interactive C shell     exec teredo   env   grep TEREDO TEREDO WORMS ukelele     If you type exit  or Control-D   then your shell exits  probably logging you out of that window  or taking you back to the previous level of shell from where the experiments started   The same mechanism works for Bash or Korn shell   You may find that the prompt after the exit commands appears in funny places     Note the discussion in the comments   This is not a solution I would recommend  but it does achieve the stated purpose of a single script to set the environment that works with all shells  that accept the -i option to make an interactive shell    You could also add      after the option to relay any other arguments  which might then make the shell usable as a general  set environment and execute command  tool   You might want to omit the -i if there are other arguments  leading to      bin ksh export TEREDO WORMS ukelele exec  SHELL     - -i      The     - -i    bit means  if the argument list contains at least one argument  use the original argument list  otherwise  substitute -i for the non-existent arguments

User · Answer

Other than writings conditionals depending on what  SHELL  TERM is set to  no   What s wrong with using Perl   It s pretty ubiquitous  I can t think of a single UNIX variant that doesn t have it   and it ll spare you the trouble

User · Answer

Technically  that is correct -- only  eval  doesn t fork another shell   However  from the point of view of the application you re trying to run in the modified environment  the difference is nil  the child inherits the environment of its parent  so the  modified  environment is conveyed to all descending processes   Ipso facto  the changed environment variable  sticks  -- as long as you are running under the parent program shell   If it is absolutely necessary for the environment variable to remain after the parent  Perl or shell  has exited  it is necessary for the parent shell to do the heavy lifting   One method I ve seen in the documentation is for the current script to spawn an executable file with the necessary  export  language  and then trick the parent shell into executing it -- always being cognizant of the fact that you need to preface the command with  source  if you re trying to leave a non-volatile version of the modified environment behind   A Kluge at best   The second method is to modify the script that initiates the shell environment   bashrc or whatever  to contain the modified parameter   This can be dangerous -- if you hose up the initialization script it may make your shell unavailable the next time it tries to launch   There are plenty of tools for modifying the current shell  by affixing the necessary tweaks to the  launcher  you effectively push those changes forward as well  Generally not a good idea  if you only need the environment changes for a particular application suite  you ll have to go back and return the shell launch script to its pristine state  using vi or whatever  afterwards   In short  there are no good  and easy  methods   Presumably this was made difficult to ensure the security of the system was not irrevocably compromised

User · Answer

You can invoke another one Bash with the different bash profile   Also  you can create special bash profile for using in multi-bashprofile environment    Remember that you can use functions inside of bashprofile  and that functions will be avialable globally  for example   function user   export USER NAME  1    can set variable in runtime  for example  user olegchir  amp  amp  env   grep olegchir

User · Answer

You could always use aliases  alias your env  source   scripts your env sh

User · Answer

Under OS X bash you can do the following   Create the bash script file to unset the variable     bin bash unset http proxy   Make the file executable  sudo chmod 744 unsetvar   Create alias  alias unsetvar  source  your path to the script unsetvar    It should be ready to use so long you have the folder containing your script file appended to the path

User · Answer

You re not going to be able to modify the caller s shell because it s in a different process context   When child processes inherit your shell s variables  they re inheriting copies themselves   One thing you can do is to write a script that emits the correct commands for tcsh or sh based how it s invoked   If you re script is  setit  then do   ln -s setit setit-sh   and  ln -s setit setit-csh   Now either directly or in an alias  you do this from sh  eval  setit-sh    or this from csh  eval  setit-csh    setit uses  0 to determine its output style   This is reminescent of how people use to get the TERM environment variable set   The advantage here is that setit is just written in whichever shell you like as in      bin bash arg0  0 arg0   arg0      for nv in      NAME1 VALUE1      NAME2 VALUE2 do    if   x arg0   xsetit-sh    then       echo  export   nv        elif   x arg0   xsetit-csh    then       echo  setenv    nv          nv             fi done   with the symbolic links given above  and the eval of the backquoted expression  this has the desired result   To simplify invocation for csh  tcsh  or similar shells   alias dosetit  eval  setit-csh     or for sh  bash  and the like   alias dosetit  eval  setit-sh     One nice thing about this is that you only have to maintain the list in one place  In theory you could even stick the list in a file and put cat nvpairfilename between  in  and  do    This is pretty much how login shell terminal settings used to be done   a script would output statments to be executed in the login shell   An alias would generally be used to make invocation simple  as in  tset vt100    As mentioned in another answer  there is also similar functionality in the INN UseNet news server

User · Answer

Add the -l flag in top of your bash script i e      usr bin env bash -l       export NAME1  VALUE1  export NAME2  VALUE2    The values with NAME1 and NAME2 will now have been exported to your current environment  however these changes are not permanent  If you want them to be permanent you need to add them to your  bashrc file or other init file    From the man pages   -l Make bash act as if it had been invoked as a login shell  see INVOCATION below

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I don t see any answer documenting how to work around this problem with cooperating processes   A common pattern with things like ssh-agent is to have the child process print an expression which the parent can eval   bash  eval   shh-agent    For example  ssh-agent has options to select Csh or Bourne-compatible output syntax   bash  ssh-agent SSH2 AUTH SOCK  tmp ssh-era ssh2-10690-agent  export SSH2 AUTH SOCK  SSH2 AGENT PID 10691  export SSH2 AGENT PID  echo Agent pid 10691     This causes the agent to start running  but doesn t allow you to actually use it  unless you now copy-paste this output to your shell prompt    Compare   bash  ssh-agent -c setenv SSH2 AUTH SOCK  tmp ssh-era ssh2-10751-agent  setenv SSH2 AGENT PID 10752  echo Agent pid 10752     As you can see  csh and tcsh uses setenv to set varibles    Your own program can do this  too    bash  foo   makefoo    Your makefoo script would simply calculate and print the value  and let the caller do whatever they want with it -- assigning it to a variable is a common use case  but probably not something you want to hard-code into the tool which produces the value

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In my  bash profile I have      No Proxy function noproxy        usr local sbin noproxy   turn off proxy server     unset http proxy HTTP PROXY https proxy HTTPs PROXY       Proxy function setproxy       sh  usr local sbin proxyon   turn on proxy server      http proxy http   127 0 0 1 8118      HTTP PROXY  http proxy     https proxy  http proxy     HTTPS PROXY  https proxy     export http proxy https proxy HTTP PROXY HTTPS PROXY     So when I want to disable the proxy   the function s  run in the login shell and sets the variables as expected and wanted

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You can instruct the child process to print its environment variables  by calling  env    then loop over the printed environment variables in the parent process and call  export  on those variables   The following code is based on Capturing output of find   -print0 into a bash array  If the parent shell is the bash  you can use  while IFS  read -r -d    0  line  do     export   line  done  lt   lt  bash -s  lt  lt  lt   export VARNAME something  env -0   echo  VARNAME   If the parent shell is the dash  then read does not provide the -d flag and the code gets more complicated  TMPDIR   mktemp -d  mkfifo  TMPDIR fifo  bash -s  lt  lt   EOF      export VARNAME something     while IFS  read -r -d    0  line  do         echo   printf   q    line       done  lt   lt  env -0  EOF    gt   TMPDIR fifo  amp  while read -r line  do export    eval echo  line    done  lt   TMPDIR fifo rm -r  TMPDIR echo  VARNAME

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This works  mdash  it isn t what I d use  but it  works    Let s create a script teredo to set the environment variable TEREDO WORMS      bin ksh export TEREDO WORMS ukelele exec  SHELL -i   It will be interpreted by the Korn shell  exports the environment variable  and then replaces itself with a new interactive shell   Before running this script  we have SHELL set in the environment to the C shell  and the environment variable TEREDO WORMS is not set     env   grep SHELL SHELL  bin csh   env   grep TEREDO     When the script is run  you are in a new shell  another interactive C shell  but the environment variable is set     teredo   env   grep TEREDO TEREDO WORMS ukelele     When you exit from this shell  the original shell takes over     exit   env   grep TEREDO     The environment variable is not set in the original shell s environment   If you use exec teredo to run the command  then the original interactive shell is replaced by the Korn shell that sets the environment  and then that in turn is replaced by a new interactive C shell     exec teredo   env   grep TEREDO TEREDO WORMS ukelele     If you type exit  or Control-D   then your shell exits  probably logging you out of that window  or taking you back to the previous level of shell from where the experiments started   The same mechanism works for Bash or Korn shell   You may find that the prompt after the exit commands appears in funny places     Note the discussion in the comments   This is not a solution I would recommend  but it does achieve the stated purpose of a single script to set the environment that works with all shells  that accept the -i option to make an interactive shell    You could also add      after the option to relay any other arguments  which might then make the shell usable as a general  set environment and execute command  tool   You might want to omit the -i if there are other arguments  leading to      bin ksh export TEREDO WORMS ukelele exec  SHELL     - -i      The     - -i    bit means  if the argument list contains at least one argument  use the original argument list  otherwise  substitute -i for the non-existent arguments

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Your shell process has a copy of the parent s environment and no access to the parent process s environment whatsoever  When your shell process terminates any changes you ve made to its environment are lost  Sourcing a script file is the most commonly used method for configuring a shell environment  you may just want to bite the bullet and maintain one for each of the two flavors of shell

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I don t see any answer documenting how to work around this problem with cooperating processes   A common pattern with things like ssh-agent is to have the child process print an expression which the parent can eval   bash  eval   shh-agent    For example  ssh-agent has options to select Csh or Bourne-compatible output syntax   bash  ssh-agent SSH2 AUTH SOCK  tmp ssh-era ssh2-10690-agent  export SSH2 AUTH SOCK  SSH2 AGENT PID 10691  export SSH2 AGENT PID  echo Agent pid 10691     This causes the agent to start running  but doesn t allow you to actually use it  unless you now copy-paste this output to your shell prompt    Compare   bash  ssh-agent -c setenv SSH2 AUTH SOCK  tmp ssh-era ssh2-10751-agent  setenv SSH2 AGENT PID 10752  echo Agent pid 10752     As you can see  csh and tcsh uses setenv to set varibles    Your own program can do this  too    bash  foo   makefoo    Your makefoo script would simply calculate and print the value  and let the caller do whatever they want with it -- assigning it to a variable is a common use case  but probably not something you want to hard-code into the tool which produces the value

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You should use modules  see http   modules sourceforge net   EDIT  The modules package has not been updated since 2012 but still works ok for the basics  All the new features  bells and whistles happen in lmod this day  which I like it more   https   www tacc utexas edu research-development tacc-projects lmod

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You re not going to be able to modify the caller s shell because it s in a different process context   When child processes inherit your shell s variables  they re inheriting copies themselves   One thing you can do is to write a script that emits the correct commands for tcsh or sh based how it s invoked   If you re script is  setit  then do   ln -s setit setit-sh   and  ln -s setit setit-csh   Now either directly or in an alias  you do this from sh  eval  setit-sh    or this from csh  eval  setit-csh    setit uses  0 to determine its output style   This is reminescent of how people use to get the TERM environment variable set   The advantage here is that setit is just written in whichever shell you like as in      bin bash arg0  0 arg0   arg0      for nv in      NAME1 VALUE1      NAME2 VALUE2 do    if   x arg0   xsetit-sh    then       echo  export   nv        elif   x arg0   xsetit-csh    then       echo  setenv    nv          nv             fi done   with the symbolic links given above  and the eval of the backquoted expression  this has the desired result   To simplify invocation for csh  tcsh  or similar shells   alias dosetit  eval  setit-csh     or for sh  bash  and the like   alias dosetit  eval  setit-sh     One nice thing about this is that you only have to maintain the list in one place  In theory you could even stick the list in a file and put cat nvpairfilename between  in  and  do    This is pretty much how login shell terminal settings used to be done   a script would output statments to be executed in the login shell   An alias would generally be used to make invocation simple  as in  tset vt100    As mentioned in another answer  there is also similar functionality in the INN UseNet news server

[bash] Can a shell script set environment variables of the calling shell?

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