I'm looking for how I might allow user input in a second command in a bash statement and I'm not sure how to go about it. I'd like to be able to provide a one-liner for someone to be able to install my application, but part of that application process requires asking some questions.
The current script setup looks like:
curl <url/to/bootstrap.sh> | bash
and then boostrap.sh does:
if [ $UID -ne 0 ]; then
echo "This script requires root to run. Restarting the script under root."
exec sudo $0 "$#"
exit $?
fi
git clone <url_to_repo> /usr/local/repo/
bash /usr/local/repo/.setup/install_system.sh
which in turn calls a python3 script that asks for input.
I know that the the curl in the first line is using stdin and so that might make what I'm asking impossible and that it has to be two lines to ever work:
wget <url/to/boostrap.sh>
bash bootstrap.sh
You can restructure your script to run this way:
bash -c "$(curl -s http://0.0.0.0//test.bash 2>/dev/null)"
foo
wololo:a
a
My test.bash is really just
#!/bin/bash
echo foo
python -c 'x = raw_input("wololo:");print(x)'`
To demonstrate that stdin can be read from in this way. Sure it creates a subshell to take care of curl but it allows you to keep reading from stdin as well.
Related
In reference to https://stackoverflow.com/a/11886837/1996022 (also shamelessly stole the title) where the question is how to capture the script's output I would like to know how I can additionally capture the scripts input. Mainly so scripts that also have user input produce complete logs.
I tried things like
exec 3< <(tee -ia foo.log <&3)
exec <&3 <(tee -ia foo.log <&3)
But nothing seems to work. I'm probably just missing something.
Maybe it'd be easier to use the script command? You could either have your users run the script with script directly, or do something kind of funky like this:
#!/bin/bash
main() {
read -r -p "Input string: "
echo "User input: $REPLY"
}
if [ "$1" = "--log" ]; then
# If the first argument is "--log", shift the arg
# out and run main
shift
main "$#"
else
# If run without log, re-run this script within a
# script command so all script I/O is logged
script -q -c "$0 --log $*" test.log
fi
Unfortunately, you can't pass a function to script -c which is why the double-call is necessary in this method.
If it's acceptable to have two scripts, you could also have a user-facing script that just calls the non-user-facing script with script:
script_for_users.sh
--------------------
#!/bin/sh
script -q -c "/path/to/real_script.sh" <log path>
real_script.sh
---------------
#!/bin/sh
<Normal business logic>
It's simpler:
#! /bin/bash
tee ~/log | your_script
The wonderful thing is your_script can be a function, command or a {} command block!
I'm new to bash and trying to understand what the script below is doing, i know -e is exit but i'm not sure what -se or what the $delimiter is for?
$delimiter = 'EOF-MY-APP';
$process = new SSH(
"ssh $target 'bash -se' << \\$delimiter".PHP_EOL
.'set -e'.PHP_EOL
.$command.PHP_EOL
.$delimiter
);
The -s options is usually used along with the curl $script_url | bash pattern. For example,
curl -L https://chef.io/chef/install.sh | sudo bash -s -- -P chefdk
-s makes bash read commands (the "install.sh" code as downloaded by "curl") from stdin, and accept positional parameters nonetheless.
-- lets bash treat everything which follows as positional parameters instead of options.
bash will set the variables $1 and $2 of the "install.sh" code to -P and to chefdk, respectively.
Reference: https://www.experts-exchange.com/questions/28671064/what-is-the-role-of-bash-s.html
From man bash:
-s If the -s option is present, or if no arguments remain after
option processing, then commands are read from the standard
input. This option allows the positional parameters to be
set when invoking an interactive shell.
From help set:
-e Exit immediately if a command exits with a non-zero status.
So, this tells bash to read the script to execute from Standard Input, and to exit immediately if any command in the script (from stdin) fails.
The delimiter is used to mark the start and end of the script. This is called a Here Document or a heredoc.
#!/bin/bash
if [ ! -f readexportfile ]; then
echo "readexportfile does not exist"
exit 0
fi
The above is part of my script. When the current shell is /bin/csh my script fails with the following error:
If: Expression Syntax
Then: Command not found
If I run bash and then run my script, it runs fine(as expected).
So the question is: If there is any way that myscript can change the current shell and then interpretate rest of the code.
PS: If i keep bash in my script, it changes the current shell and rest of the code in script doesn't get executed.
The other replies are correct, however, to answer your question, this should do the trick:
[[ $(basename $SHELL) = 'bash' ]] || exec /bin/bash
The exec builtin replaces the current shell with the given command (in this case, /bin/bash).
You can use SHEBANG(#!) to overcome your issue.
In your code you are already using she-bang but make sure it is first and foremost line.
$ cat test.sh
#!/bin/bash
if [ ! -f readexportfile ]; then
echo "readexportfile does not exist"
exit 0
else
echo "No File"
fi
$ ./test.sh
readexportfile does not exist
$ echo $SHELL
/bin/tcsh
In the above code even though I am using CSH that code executed as we mentioned shebang in the code. In case if there is no shebang then it will take the help of shell in which you are already logged in.
In you case you also check the location of bash interpreter using
$ which bash
or
$ cat /etc/shells |grep bash
Is it possible for a shell script to test whether it was executed through source? That is, for example,
$ source myscript.sh
$ ./myscript.sh
Can myscript.sh distinguish from these different shell environments?
I think, what Sam wants to do may be not possible.
To what degree a half-baken workaround is possible, depends on...
...the default shell of users, and
...which alternative shells they are allowed to use.
If I understand Sam's requirement correctly, he wants to have a 'script',
myscript, that is...
...not directly executable via invoking it by its name myscript
(i.e. that has chmod a-x);
...not indirectly executable for users by invoking sh myscript or
invoking bash myscript
...only running its contained functions and commands if invoked by
sourcing it: . myscript
The first things to consider are these
Invoking a script directly by its name (myscript) requires a first line in
the script like #!/bin/bash or similar. This will directly determine which
installed instance of the bash executable (or symlink) will be invoked to run
the script's content. This will be a new shell process. It requires the
scriptfile itself to have the executable flag set.
Running a script by invoking a shell binary with the script's (path+)name as
an argument (sh myscript), is the same as '1.' -- except that the
executable flag does not need to be set, and said first line with the
hashbang isn't required either. The only thing needed is that the invoking
user needs read access to the scriptfile.
Invoking a script by sourcing its filename (. myscript) is very much the
same as '1.' -- exept that it isn't a new shell that is invoked. All the
script's commands are executed in the current shell, using its environment
(and also "polluting" its environment with any (new) variables it may set or
change. (Usually this is a very dangerous thing to do: but here it could be
used to execute exit $RETURNVALUE under certain conditions....)
For '1.':
Easy to achieve: chmod a-x myscript will prevent myscript from being
directly executable. But this will not fullfill requirements '2.' and '3.'.
For '2.' and '3.':
Much harder to achieve. Invokations by sh myscript require reading
privileges for the file. So an obvious way out would seem to chmod a-r
myscript. However, this will also dis-allow '3.': you will not be able to
source the script either.
So what about writting the script in a way that uses a Bashism? A Bashism is a
specific way to do something which other shells do not understand: using
specific variables, commands etc. This could be used inside the script to
discover this condition and "do something" about it (like "display warning.txt",
"mailto admin" etc.). But there is no way in hell that this will prevent sh or
bash or any other shell from reading and trying to execute all the following
commands/lines written into the script unless you kill the shell by invoking
exit.
Examples: in Bash, the environment seen by the script knows of $BASH,
$BASH_ARGV, $BASH_COMMAND, $BASH_SUBSHELL, BASH_EXECUTION_STRING... . If
invoked by sh (also if sourced inside a sh), the executing shell will see
all these $BASH_* as empty environment variables. Again, this could be used
inside the script to discover this condition and "do something"... but not
prevent the following commands from being invoked!
I'm now assuming that...
...the script is using #!/bin/bash as its first line,
...users have set Bash as their shell and are invoking commands in the
following table from Bash and it is their login shell,
...sh is available and it is a symlink to bash or dash.
This will mean the following invokations are possible, with the listed values
for environment variables
vars+invok's | ./scriptname | sh scriptname | bash scriptname | . scriptname
---------------+--------------+---------------+-----------------+-------------
$0 | ./scriptname | ./scriptname | ./scriptname | -bash
$SHLVL | 2 | 1 | 2 | 1
$SHELLOPTS | braceexpand: | (empty) | braceexpand:.. | braceexpand:
$BASH | /bin/bash | (empty) | /bin/bash | /bin/bash
$BASH_ARGV | (empty) | (empty) | (empty) | scriptname
$BASH_SUBSHELL | 0 | (empty) | 0 | 0
$SHELL | /bin/bash | /bin/bash | /bin/bash | /bin/bash
$OPTARG | (empty) | (empty) | (emtpy) | (emtpy)
Now you could put a logic into your text script:
If $0 is not equal to -bash, then do an exit $SOMERETURNVALUE.
In case the script was called via sh myscript or bash myscript, then it will
exit the calling shell. In case it was run in the current shell, it will
continue to run. (Warning: in case the script has any other exit statements,
your current shell will be 'killed'...)
So put into your non-executable myscript.txt near its beginning something like
this may do something close to your goal:
echo BASH=$BASH
test x${BASH} = x/bin/bash && echo "$? : FINE.... You're using 'bash ...'"
test x${BASH} = x/bin/bash || echo "$? : RATS !!! -- You're not using BASH and I will kick you out!"
test x${BASH} = x/bin/bash || exit 42
test x"${0}" = x"-bash" && echo "$? : FINE.... You've sourced me, and I'm your login shell."
test x"${0}" = x"-bash" || echo "$? : RATS !!! -- You've not sourced me (or I'm not your bash login shell) and I will kick you out!"
test x"${0}" = x"-bash" || exit 33
This may or may not be what the asker wanted but, on a similar situation, I wanted a script to indicate that it is meant to be sourced and not directly run.
To achieve this effect my script reads:
#!/bin/echo Should be run as: source
export SOMEPATH="/some/path/on/my/system"
echo "Your environment has been set up"
So when I run it either as a command or sourced I get:
$ ./myscript.sh
Should be run as: source ./myscript.sh
$ source ./myscript.sh
Your environment has been set up
You can of course fool the script by running it as sh ./myscript.sh, but at least it gives the correct expected behaviour on 2 out of 3 cases.
This is what I was looking for:
[[ ${BASH_SOURCE[0]} = $0 ]] && main "$#"
I cannot add comment yet (stackexchange policies) so I add my own answer:
This one may works regardless if we do:
bash scriptname
scriptname
./scriptname.
on both bash and mksh.
if [ "${0##/*}" == scriptname ] # if the current name is our script
then
echo run
else
echo sourced
fi
If you have a non-altering file path for regular users, then:
if [ "$(/bin/readlink -f "$0")" = "$KNOWN_PATH_OF_THIS_FILE" ]; then
# the file was executed
else
# the file was sourced
fi
(it can also easily be loosened to only check for the filename or whatever).
But your users need to have read permission to be able to source the file, so absolutely nothing can stop them from doing what they want with the file. But it might help them out to not use it in the wrong way.
This solution is not dependent on Bashisms.
Yes it is possible. In general you can do the following:
#! /bin/bash
sourced () {
echo Sourced
}
executed () {
echo Executed
}
if [[ ${0##*/} == -* ]]; then
sourced
else
executed $#
fi
Giving the following output:
$ ./myscript
Executed
$ . ./myscript
Sourced
Based on Kurt Pfeifle’s answer, this works for me
if [ $SHLVL = 1 ]
then
echo 'script was sourced'
fi
Example
Since all of our machines have history, I did this:
check_script_call=$(history |tail -1|grep myscript.sh )
if [ -z "$check_script_call" ];then
echo "This file should be called as a source."
echo "Please, try again this way:"
echo "$ source /path/to/myscript.sh"
exit 1
fi
Everytime you run a script (without source), your shell creates a new env without history.
If you want to care about performance you can try this:
if ! history |tail -1|grep set_vars ;then
echo -e "This file should be called as a source.\n"
echo "Please, try again this way:"
echo -e "$ source /path/to/set_vars\n"
exit 1
fi
PS: I think Kurt's answer is much more complete but I think this could help.
In the first case, $0 will be "myscript.sh". In the second case, it will be "./myscript". But, in general, there's no way to tell source was used.
If you tell us what you're trying to do, instead of how you want to do it, a better answer might be forthcoming.
In a C program I can write argv[0] and the new name shows up in a ps listing.
How can I do this in bash?
You can do it when running a new program via exec -a <newname>.
Just for the record, even though it does not exactly answer the original poster's question, this is something trivial to do with zsh:
ARGV0=emacs nethack
I've had a chance to go through the source for bash and it does not look like there is any support for writing to argv[0].
I'm assuming you've got a shell script that you wish to execute such that the script process itself has a new argv[0]. For example (I've only tested this in bash, so i'm using that, but this may work elsewhere).
#!/bin/bash
echo "process $$ here, first arg was $1"
ps -p $$
The output will be something like this:
$ ./script arg1
process 70637 here, first arg was arg1
PID TTY TIME CMD
70637 ttys003 0:00.00 /bin/bash ./script arg1
So ps shows the shell, /bin/bash in this case. Now try your interactive shell's exec -a, but in a subshell so you don't blow away the interactive shell:
$ (exec -a MyScript ./script arg1)
process 70936 here, first arg was arg1
PID TTY TIME CMD
70936 ttys008 0:00.00 /bin/bash /path/to/script arg1
Woops, still showing /bin/bash. what happened? The exec -a probably did set argv[0], but then a new instance of bash started because the operating system read #!/bin/bash at the top of your script. Ok, what if we perform the exec'ing inside the script somehow? First, we need some way of detecting whether this is the "first" execution of the script, or the second, execed instance, otherwise the second instance will exec again, and on and on in an infinite loop. Next, we need the executable to not be a file with a #!/bin/bash line at the top, to prevent the OS from changing our desired argv[0]. Here's my attempt:
$ cat ./script
#!/bin/bash
__second_instance="__second_instance_$$"
[[ -z ${!__second_instance} ]] && {
declare -x "__second_instance_$$=true"
exec -a MyScript "$SHELL" "$0" "$#"
}
echo "process $$ here, first arg was $1"
ps -p $$
Thanks to this answer, I first test for the environment variable __second_instance_$$, based on the PID (which does not change through exec) so that it won't collide with other scripts using this technique. If it's empty, I assume this is the first instance, and I export that environment variable, then exec. But, importantly, I do not exec this script, but I exec the shell binary directly, with this script ($0) as an argument, passing along all the other arguments as well ($#). The environment variable is a bit of a hack.
Now the output is this:
$ ./script arg1
process 71143 here, first arg was arg1
PID TTY TIME CMD
71143 ttys008 0:00.01 MyScript ./script arg1
That's almost there. The argv[0] is MyScript like I want, but there's that extra arg ./script in there which is a consequence of executing the shell directly (rather than via the OS's #! processing). Unfortunately, I don't know how to get any better than this.
Update for Bash 5.0
Looks like Bash 5.0 adds support for writing to special variable BASH_ARGV0, so this should become far simpler to accomplish.
(see release announcement)
( exec -a foo bash -c 'echo $0' )
ps and others inspect two things, none of which is argv0: /proc/PID/comm (for the "process name") and /proc/PID/cmdline (for the command-line). Assigning to argv0 will not change what ps shows in the CMD column, but it will change what the process usually sees as its own name (in output messages, for example).
To change the CMD column, write to /proc/PID/comm:
echo -n mynewname >/proc/$$/comm; ps
You cannot write to or modify /proc/PID/cmdline in any way.
Process can set their own "title" by writing to the memory area in which argv & envp are located (note that this is different than setting BASH_ARGV0). This has the side effect of changing /proc/PID/cmdline as well, which is what some daemons do in order to prettify (hide?) their command lines. libbsd's setproctitle() does exactly that, but you cannot do that in Bash without support of external tools.
I will just add that this must be possible at runtime, at least in some environments. Assigning $0 in perl on linux does change what shows up in ps. I do not know how that is implemented, however. If I can find out, i'll update this.
edit:
Based on how perl does it, it is non-trivial. I doubt there is any bask built in way at runtime but don't know for sure. You can see how perl does sets the process name at runtime.
Copy the bash executable to a different name.
You can do this in the script itself...
cp /bin/bash ./new-name
PATH=$PATH:.
exec new-name $0
If you are trying to pretend you are not a shell script you can rename the script itself to something cool or even " " (a single space) so
exec new-name " "
Will execute bash your script and appears in the ps list as just new-name.
OK so calling a script " " is a very bad idea :)
Basically, to change the name
bash script
rename bash and rename the script.
If you are worried, as Mr McDoom. apparently is, about copying a binary to a new name (which is entirely safe) you could also create a symlink
ln -s /bin/bash ./MyFunkyName
./MyFunkyName
This way, the symlink is what appears in the ps list. (again use PATH=$PATH:. if you dont want the ./)