I am trying to use environment variables set by ksh and the expect command in the same script. However, if I try to source both of them, it doesnt work. Is there a way to source ksh and expect in the same script?
Do something like
#!/usr/bin/ksh
. /path/to/ksh_stuff.sh
export FOO=bar
# other ksh stuff
expect <<'END_EXPECT'
source /path/to/expect_stuff.exp
send_user "FOO is $env(FOO)\n"
# other expect stuff
END_EXPECT
Adding quotes around the here-doc terminator (<<'END_EXPECT') means that the entire here-doc is single quoted, so ksh will not attempt any parameter substitutions on it. This is a effective way to isolate the expect script's variables from ksh.
In Korn shell you dot in the other script, example:
. ${other_script}
This will run in the same process as the parent script. The other script can see any variables that are defined in the parent script. If you want to sub-shell (to run an external command), then you will need to export any variables first.
If you want to reference environment variables in your expect script, (those that are exported by a ksh script that runs expect in a subshell) then your expect script needs to reference a global array env . For example if your ksh script exports MYPATH variable then subshells to expect, the expect might reference $env(MYPATH)
Related
I wasn't able to find a documentation for the widely used autoload command in zsh. Does anybody can explain it in plain English?
A bit more specific: What does autoloading of modules mean, for example in this line:
autoload -Uz vcs_info
What does it do?
I've tried autoload --help, man autoload, googling - no success. Thanks!
The autoload feature is not available in bash, but it is in ksh (korn shell) and zsh. On zsh see man zshbuiltins.
Functions are called in the same way as any other command. There can be a name conflict between a program and a function. What autoload does is to mark that name as being a function rather than an external program. The function has to be in a file on its own, with the filename the same as the function name.
autoload -Uz vcs_info
The -U means mark the function vcs_info for autoloading and suppress alias expansion. The -z means use zsh (rather than ksh) style. See also the functions command.
Edit (from comment, as suggested by #ijoseph):
So it records the fact that the name is a function and not an external program - it does not call it unless the -X option is used, it just affects the search path when it is called. If the function name does not collide with the name of a program then it is not required. Prefix your functions with something like f_ and you will probably never need it.
For more detail see http://zsh.sourceforge.net/Doc/Release/Functions.html.
autoload tells zsh to look for a file in $FPATH/$fpath containing a function definition, instead of a file in $PATH/$path containing an executable script or binary.
Script
A script is just a sequence of commands that get executed when the script is run. For example, suppose you have a file called hello like this:
echo "Setting 'greeting'"
greeting='Hello'
If the file is executable and located in one of the directories in your $PATH, then you can run it as a script by just typing its name. But scripts get their own copy of the shell process, so anything they do can't affect the calling shell environment. The assignment to greeting above will be in effect only within the script; once the script exits, it won't have had any impact on your interactive shell session:
$ hello
Setting 'greeting'
$ echo $greeting
$
Function
A function is instead defined once and stays in the shell's memory; when you call it, it executes inside the current shell, and can therefore have side effects:
hello() {
echo "Setting 'greeting'"
greeting='Hello'
}
$ hello
Setting 'greeting'
$ echo $greeting
Hello
So you use functions when you want to modify your shell environment. The Zsh Line Editor (ZLE) also uses functions - when you bind a key to some action, that action is defined as a shell function (which has to be added to ZLE with the zle -N command).
Now, if you have a lot of functions, then you might not want to define all of them in your .zshrc every time you start a new shell; that slows down shell startup and uses memory to store functions that you might not wind up calling during the lifetime of that shell. So you can instead put the function definitions into their own files, named after the functions they define, and put the files into directories in your $FPATH, which works like $PATH.
Zsh comes with a bunch of standard functions in the default $FPATH already. But it won't know to look for a command there unless you've first told it that the command is a function.
That's what autoload does: it says "Hey, Zsh, this command name here is a function, so when I try to run it, go look for its definition in my FPATH, instead of looking for an executable in my PATH."
The first time you run command which Zsh determines is autoloaded function, the shell sources the definition file. Then, if there's nothing in the file except the function definition, or if the shell option KSH_AUTOLOAD is set, it proceeds to call the function with the arguments you supplied. But if that option is not set and the file contains any code outside the function definition (like initialization of variables used by the function), the function is not called automatically. In that case it's up to you to call the function inside the file after defining it so that first invocation will work.
When I use the command typeset -f in ksh, a list of functions with their definition is displayed in stdout.
I tried to search where those functions are defined, but I couldn't find any hint about them. Can anyone help me finding them?
EDIT
I'm just learning the use of the typeset command, typing man typeset game me nothing (no manual entry for typeset).
In order to define functions that will be displayed using typeset -f, we need to define a function and export it using typeset -xf.
Functions can be declared in the .profile, or files called from .profile or put in a dir that is referenced by the FPATH variable (and proabably other places too). Read your man ksh carefully for the order of files that are processed on startup. Search for the 'Invocation', 'Files', and 'Functions' sections.
Also, there are a group of default functions that ksh sets up. So please edit your question to show the function names that your concerned with.
IHTH
Shells don't keep a record of where functions (or aliases, or variables, etc...) are defined. Conceptually, and notwithstanding interactive usage features like shell history, shells read commands from input one at a time, execute them, and then forget them. Sometimes those commands come from interactive input, sometimes they come from scripts. Sometimes they have side effects like defining a function in the shell's environment, but the shell still doesn't remember the command or its position in the shell's input stream after it's finished executing it.
Any variable that I declare in my zshrc is available in the shell as an environment variable. I don't want this to happen.
I tried putting the variables in a function and setting them as local, but then the function is available outside of the zshrc.
How can I make it so what happens in my zshrc stays in my zshrc?
If you're using a recent version of zsh you can use an anonymous function:
function () {
local xyz=abc
# whatever
}
The function will be automatically executed and then thrown away, it exists only for scoping purposes.
This works for any sourced file, not only zshrc.
They are available, but they are not exported so scripts launching from command-line don’t get these variables. If your .zshrc looks like
function zshrc()
{
local VAR=1
# Do stuff
}
zshrc
and you then never want to launch zshrc function again you can just do
unfunction zshrc
afterwards.
If you do not prefix a variable with the word local it will remain until you do one of the following:
Open a new terminal window.
Run exec zsh or exec bash depending on your shell. This just clears out your local variables that were not assigned with the word local.
Avoid this
method_name(){
a=11
echo $a
}
Correct Example
method_name(){
local a=11
echo $a
}
This variable is scoped to the function name method_name and only available inside of the function when called (and not afterwards).
If you want direct access to that local variable you can set it this way
local z=11
And call it this way
echo $z
Additionally, environment variables are different from local variables
Depending on your shell and needs, you may use .bash_profile or .bashrc or .zshrc etc. to store functions and aliases.
View this reference for more on environment variables and their respective shells
Also read this to understand how to set environment variables on the command line using shell expansions
You can quickly view environment variables with env or printenv
The convention is to use UPPERCASE
To temporarily set an environment variable (stored until you close the terminal)
export A=11 or export B="11 is part of this string"
Assuming you have opened a new terminal window or sourced .zshrc or .bashrc or whichever you are using you can now use this environment variable until you close your terminal session. Note: do not use $ when setting, but do use $ when referencing the variable.
Examples
echo "A is equal to: $A and that is pretty nice"
echo "$A"
How to source a file
source ~/path/to/file/filename
Example
source ~/.bash_profile
To set an environment variable (until you remove it or set it again)
Use the code above but place it in your ~/.bash_profile or ~/.zshrc or other respective file. Save the file and source it.
Example
export B="11 is part of this string"
You now can view it with
env
To remove that environment variable, remove it from the file and again source the file.
To temporarily remove an environmental variable, use unset
Example
unset B
Note there is no $ when unsetting.
To set environment variables from the command line
export BLABLA="environment variable set from the command line, saved in file for later use"
Check the file you are sending it to, it may not start on a new line, it might have been concatenated to your last line which was some other function, alias or other.
This is not a fully comprehensive answer, but it is a great step in the right direction. It shows how scope in a terminal shell can be set, used and removed.
There is apparently a bash convention to name 'private' functions with double underscore .. of course they are not actually private . I am using this convention in my .zshrc.
function __comment()
{
curr=`pwd`
echo "$curr $*"
}
__comment 'Here is a Comment'
I want to use a shell script that I can call to set some environment variables. However, after the execution of the script, I don't see the environment variable using "printenv" in bash.
Here is my script:
#!/bin/bash
echo "Hello!"
export MYVAR=boubou
echo "After setting MYVAR!"
When I do "./test.sh", I see:
Hello!
After setting MYVAR!
When I do "printenv MYVAR", I see nothing.
Can you tell me what I'm doing wrong?
This is how environment variables work. Every process has a copy of the environment. Any changes that the process makes to its copy propagate to the process's children. They do not, however, propagate to the process's parent.
One way to get around this is by using the source command:
source ./test.sh
or
. ./test.sh
(the two forms are synonymous).
When you do this, instead of running the script in a sub-shell, bash will execute each command in the script as if it were typed at the prompt.
Another alternative would be to have the script print the variables you want to set, with echo export VAR=value and do eval "$(./test.sh)" in your main shell. This is the approach used by various programs [e.g. resize, dircolors] that provide environment variables to set.
This only works if the script has no other output (or if any other output appears on stderr, with >&2)
Is there any way to find out the variables available in the scope of the shell script.
the scenario is like this, we are using some third party tools and we can customize the output with creating shell scripts with a particular naming convention. we know that certain parameters are being passed to our custom shell scripts but we want to know what else is being passed.
thanks.
The command is set
From the bash manual page
set [--abefhkmnptuvxBCHP] [-o option] [arg ...]
Without options, the name and value of each shell variable are displayed in a
format that can be reused as input.
Do not confuse this with env which will print out the values of environment variables not shell variables. shell variables can be marked for automatic export into the environment of subsequent child processes using the export command.
scope as a programming term, only really applies to shell variables - commands like typeset and local can be used in some shells (ksh and bash) to allow the use of scoped shell variables within functions. environment variables are global to a instance of a processes.
It's very easy ;)
env
It sounds like you want environment variables, so use export -p. The output (which consists of lines of the form export variable=value per POSIX) is quoted in such a way that it can be parsed by the shell. It's also sorted by variable name in most shells.
If you want all shell parameters (for your use case, this would be relevant only if the scripts were sourced rather than called as separate programs), use set (again, it's in POSIX, the output is properly quoted for reparsing, and it's sorted in most shells).
This may be really simplistic but...
grep = <your script>