I have a command which is run with the system command.
Could I log what is passed to the shell?
P.S. I've got the problems with qoutes =)
You mentioned having "the problem with the quotes". I assume you mean double quotes? Modify Vapire's solution to this:
command = %Q{echo "double quoted string"} # store the command as string
puts command # print it before you execute it
system(command) # execute it in the shell
You can simply print the string before you're sending it to system command
command = "whoami" # store the command as string
puts command # print it before you execute it
system(command) # execute it in the shell
Related
I want to execute program by 'ruby -e' but it executes program if it's in single line but it's not executing if it's multiple line and throws the error. For an example,
>ruby -e "puts 'rajagopalan'"
=>rajagopalan
but
>ruby -e "a=[1,2,3,4,5]
a.each do |i|
puts i
end
"
it throws the error that "a.each do |i|
The syntax of the command is incorrect.
"
Can someone guide me how to execute the mulitiline via ruby -e
I have attached image here
you can try here document in your shell command:
ruby <<END
a=[1,2,3,4,5]
a.each do |i|
puts i
end
END
Hope this helps....
Try this:
>ruby -e "a=[1,2,3,4,5]; a.each do |i| puts i; end"
Basic idea, use a semi-colon wherever a new-line would be needed.
This has nothing to do with Ruby. You need to read the manual of your terminal emulator and your shell and figure out how to escape newlines.
As can be seen in the error you posted, you get a shell prompt after the first line, so the shell clearly seems to think the command is finished. Ergo, the shell tries to interpret the Ruby commands as shell commands, which leads to the error.
As an example, I am trying to capture the raw commands that are output by the following script:
https://github.com/adampointer/go-deribit/blob/master/scripts/generate-models.sh
I have tried to following a previous answer:
BASH: echoing the last command run
but the output I am getting is as follows:
last command is gojson -forcefloats -name="${struct}" -tags=json,mapstructure -pkg=${p} >> models/${p}/${name%.*}_request.go
What I would like to do is capture the raw command, in other words have variables such as ${struct}, ${p} and ${p}/${name%.*} replaced by the actual values that were used.
How do I do this?
At the top of the script after the hashbang #!/usr/bin/env bash or #!/bin/bash (if there is any) add set -x
set -x Print commands and their arguments as they are executed
Run the script in debug mode which will trace all the commands in the script: https://stackoverflow.com/a/10107170/988525.
You can do that without editing the script by typing "bash generate-models.sh -x".
Hey am new to bash scripts and was wondering how would I capture the output of the ssh command into a bash variable? I looked around and cant seem to get it right. I have tried puts $expect_out(buffer) but when echo it says variable does not exist
I know the response should be just one line and if I want to save that into a variable response and then echo it how would I do that?
A generic idea can be something like as below.
spawn the ssh session
make proper login
Send each commands with send
Wait for desired output with expect
Example:
spawn ssh $user#$domain
expect "password" { send "$pwd\r"}
expect "#"; # This '#' is nothing but the terminal prompt
send "$cmd\r"
expect "#"
puts $expect_out(buffer); #Will print the output of the 'cmd' output now.
The word to wait for after executing the command can vary based on your system. It can be # or $ or > or :; So, make sure you are giving the correct one. Or, you can provide a generalized pattern for the prompt as such
set prompt "#|>|:|\\\$"; # We escaped the `$` symbol with backslash to match literal '$'
While using the expect after sending the commands, it can be used as
expect -re $prompt; #Using regex to match the pattern`
I would like to execute a number of bash commands from a Rakefile.
I have tried the following in my Rakefile
task :hello do
%{echo "World!"}
end
but upon executing rake hello there is no output?
How do I execute bash commands from a Rakefile?
NOTE:This is not a duplicate as it's specifically asking how to execute bash commands from a Rakefile.
I think the way rake wants this to happen is with: http://rubydoc.info/gems/rake/FileUtils#sh-instance_method
Example:
task :test do
sh "ls"
end
The built-in rake function sh takes care of the return value of the command (the task fails if the command has a return value other than 0) and in addition it also outputs the commands output.
There are several ways to execute shell commands in ruby. A simple one (and probably the most common) is to use backticks:
task :hello do
`echo "World!"`
end
Backticks have a nice effect where the standard output of the shell command becomes the return value. So, for example, you can get the output of ls by doing
shell_dir_listing = `ls`
But there are many other ways to call shell commands and they all have benefits/drawbacks and work differently. This article explains the choices in detail, but here's a quick summary possibilities:
stdout = %x{cmd} - Alternate syntax for backticks, behind the scenes
it's doing the same thing
exec(cmd) - Completely replace the running process with a new cmd process
success = system(cmd) - Run a subprocess and return true/false
on success/failure (based on cmd exit status)
IO#popen(cmd) { |io| } - Run a subprocess and connect stdout and
stderr to io
stdin, stdout, stderr = Open3.popen3(cmd) - Run a subprocess and
connect to all pipes (in, out, err)
Given that the consensus seems to prefer rake's #sh method, but OP explicitly requests bash, this answer may have some use.
This is relevant since Rake#sh uses the Kernel#system call to run shell commands. Ruby hardcodes that to /bin/sh, ignoring the user's configured shell or $SHELL in the environment.
Here's a workaround which invokes bash from /bin/sh, allowing you to still use the sh method:
task :hello_world do
sh <<-EOS.strip_heredoc, {verbose: false}
/bin/bash -xeu <<'BASH'
echo "Hello, world!"
BASH
EOS
end
class String
def strip_heredoc
gsub(/^#{scan(/^[ \t]*(?=\S)/).min}/, ''.freeze)
end
end
#strip_heredoc is borrowed from rails:
https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/string/strip.rb
You could probably get it by requiring active_support, or maybe it's autoloaded when you're in a rails project, but I was using this outside rails and so had to def it myself.
There are two heredocs, an outer one with the markers EOS and an inner one with the markers BASH.
The way this works is by feeding the inside heredoc between the BASH markers to bash's stdin. Note that it is running within the context of /bin/sh, so it's a posix heredoc, not a ruby one. Normally that requires the end marker to be in column 1, which isn't the case here because of the indenting.
However, because it's wrapped within a ruby heredoc, the strip_heredoc method applied there de-indents it, placing the entirety of the left side of the inner heredoc in column 1 prior to /bin/sh seeing it.
/bin/sh also would normally expand variables within the heredoc, which could interfere with the script. The single quotes around the start marker, 'BASH', tell /bin/sh not to expand anything inside the heredoc before it is passed to bash.
However /bin/sh does still apply escapes to the string before passing it to bash. That means backslash escapes have to be doubled to make it through /bin/sh to bash, i.e. \ becomes \\.
The bash options -xeu are optional.
The -eu arguments tell bash to run in strict mode, which stops execution upon any failure or reference to an undefined variable. This will return an error to rake, which will stop the rake task. Usually, this is what you want. The arguments can be dropped if you want normal bash behavior.
The -x option to bash and {verbose: false} argument to #sh work in concert so that rake only prints the bash commands which are actually executed. This is useful if your bash script isn't meant to run in its entirety, for example, if it has a test which allows it to exit gracefully early in the script.
Be careful to not set an exit code other than 0 if you don't want the rake task to fail. Usually, that means you don't want to use any || exit constructs without setting the exit code explicitly, i.e. || exit 0.
%{echo "World!"} defines a String. I expect you wanted %x{echo "World!"}.
%x{echo "World!"} executes the command and returns the output (stdout). You will not see the result. But you may do:
puts %x{echo "World!"}
There are more ways to call a system command:
Backticks: `
system( cmd )
popen
Open3#popen3
There are two ways:
sh " expr "
or
%x( expr )
Mind that ( expr ) can be { expr } , | expr | or ` expr `
The difference is, sh "expr" is a ruby method to execute something, and %x( expr ) is the ruby built-in method. The result and action are different. Here is an example
task :default do
value = sh "echo hello"
puts value
value = %x(echo world)
puts value
end
get:
hello # from sh "echo hello"
true # from puts value
world # from puts value
You can see that %x( expr ) will only do the shell expr but the stdout will not show in the screen. So, you'd better use%x( expr ) when you need the command result.
But if you just want to do a shell command, I recommend you use sh "expr". Because sh "irb" will make you go into the irb shell, while %x(irb) will dead.
I have a rake task that runs, quite a lot of code. At the end, I need to use sftp and ssh to do some stuff. At the moment I'm unable to automate it. Is there a way to pass to stdout?
This seems like a simple question but I can't find the answer anywhere
#some ruby code
#more ruby code
sh "sftp myuser#hots" #this opens the sftp console
sh "put file" #this doesn't get run until sftp is exited
sh "put another_file" #neither does this
#more ruby code
sh "ssh host" # opens the ssh console
sh "some_action_on_host" # this doesn't get run until ssh is exited
I know there will be ways of doing sftp and ssh using ruby but ideally I just want to be able to pipe variables and commands into the console
So you want to run sftp and send a series of commands to it? How about something like:
sftp = IO.popen("sftp myuser#hots", "w+")
sftp << "put file\n"
sftp << "put another file\n"
sftp.flush # make sure to include this
If you don't want to use ruby, then you may want to enclose your shell commands into ` (backtick characters). This string will be passed to Kernel.` method. This method execute the text as an OS shell command and returns the command's output as a string, e.g.:
`ls`
Alternative syntax to ` is %x[]. This way you can write any bash script:
%x[sftp myuser#hots <<COMMAND
put #{file}
quit
COMMAND]
Please note that this syntax support ruby expressions interpolation using #{...} syntax (similar to double-quoted string literals).