I have a bash script that employs the read command to read arguments to commands interactively, for example yes/no options. Is there a way to call this script in a non-interactive script passing default option values as arguments?
It's not just one option that I have to pass to the interactive script.
Many ways
pipe your input
echo "yes
no
maybe" | your_program
redirect from a file
your_program < answers.txt
use a here document (this can be very readable)
your_program << ANSWERS
yes
no
maybe
ANSWERS
use a here string
your_program <<< $'yes\nno\nmaybe\n'
For more complex tasks there is expect ( http://en.wikipedia.org/wiki/Expect ).
It basically simulates a user, you can code a script how to react to specific program outputs and related stuff.
This also works in cases like ssh that prohibits piping passwords to it.
You can put the data in a file and re-direct it like this:
$ cat file.sh
#!/bin/bash
read x
read y
echo $x
echo $y
Data for the script:
$ cat data.txt
2
3
Executing the script:
$ file.sh < data.txt
2
3
Just want to add one more way. Found it elsewhere, and is quite simple.
Say I want to pass yes for all the prompts at command line for a command "execute_command", Then I would simply pipe yes to it.
yes | execute_command
This will use yes as the answer to all yes/no prompts.
You can also use printf to pipe the input to your script.
var=val
printf "yes\nno\nmaybe\n$var\n" | ./your_script.sh
Related
I have a bash script that employs the read command to read arguments to commands interactively, for example yes/no options. Is there a way to call this script in a non-interactive script passing default option values as arguments?
It's not just one option that I have to pass to the interactive script.
Many ways
pipe your input
echo "yes
no
maybe" | your_program
redirect from a file
your_program < answers.txt
use a here document (this can be very readable)
your_program << ANSWERS
yes
no
maybe
ANSWERS
use a here string
your_program <<< $'yes\nno\nmaybe\n'
For more complex tasks there is expect ( http://en.wikipedia.org/wiki/Expect ).
It basically simulates a user, you can code a script how to react to specific program outputs and related stuff.
This also works in cases like ssh that prohibits piping passwords to it.
You can put the data in a file and re-direct it like this:
$ cat file.sh
#!/bin/bash
read x
read y
echo $x
echo $y
Data for the script:
$ cat data.txt
2
3
Executing the script:
$ file.sh < data.txt
2
3
Just want to add one more way. Found it elsewhere, and is quite simple.
Say I want to pass yes for all the prompts at command line for a command "execute_command", Then I would simply pipe yes to it.
yes | execute_command
This will use yes as the answer to all yes/no prompts.
You can also use printf to pipe the input to your script.
var=val
printf "yes\nno\nmaybe\n$var\n" | ./your_script.sh
I want to save a command to a file (for example I want to save the string "cat /etc/passwd" to a file) but I can't use the echo command.
How can I create and save string to a file directly without using echo command?
You can redirect cat to a file, type the text, and press Control-D when you're done, like this:
cat > file.txt
some text
some more text
^D
By ^D I mean to press Control-D at the end. The line must be empty.
It will not be part of the file, it is just to terminate the input.
Are you avoiding ECHO for security purposes (e.g. you're using a shared terminal and you don't want to leave trace in the shell history of what you've written inside your files) or you're just curious for an alternative method?
Simple alternative to echo:
As someone said, redirecting cat is probably the simpler way to go.
I'd suggest you to manually type your end-of-file, like this:
cat <<EOF > outputfile
> type here
> your
> text
> and finish it with
> EOF
Here's the string you're asking for, as an example:
cat <<EOF > myscript.sh
cat /etc/passwd
EOF
You probably don't want everyone to know you've peeked into that file, but if that's your purpose please notice that wrapping it inside an executable file won't make it more private, as that lines will be logged anyway...
Security - Avoiding history logs etc..
In modern shell, just try adding a space at the beginning of every command and use freely whatever you want.
BTW, my best hint is to avoid using that terminal at all, if you can. If you got two shells (another machine or even just another secure user in the same machine), I'd recommend you using netcat. See here: http://www.thegeekstuff.com/2012/04/nc-command-examples/?utm_source=feedburner
{ { command ls $(dirname $(which cat)) |
grep ^ca't$'; ls /etc/passwd; } |
tr \\n ' '; printf '\n'; } > output-file
But it's probably a lot simpler to just do : printf 'cat /etc/passwd\n'
To be clear, this is a tongue-in-cheek solution. The initial command is an extraordinarily convoluted way to get what you want, and this is intended to be a humorous answer. Perhaps instructive to understand.
I am not sure I understood you correctly but
cat /etc/passwd > target.file
use the > operator to write it to file without echoing
If you need to use it, inside a program :
cat <<EOF >file.txt
some text
some more text
EOF
I would imagine that you are probably trying to print the content of a string to a file, hence you mentioned echo.
You are avoiding this:
echo "cat /etc/passwd" > target.file
You can use a here string combined with cat.
cat > target.file <<< "cat /etc/passwd"
Now the file target.file will contain a string cat /etc/passwd.
$ cat target.file
cat /etc/passwd
$
To create string:
var1=your command
to save a file or variable in a file without echo use:
cat $FILE/VAR1 > /new/file/path
This question already has answers here:
Passing arguments to an interactive program non-interactively
(5 answers)
Closed 7 years ago.
So suppose a normal command run in terminal goes like this....
user$ thecommand
Please enter your first name:
>
and then waits for your to type your name... straightforward, but if in a bash script I try and do something like:
#! /bin/bash
echo "What is your name?"
read name
thecommand
how would I have THE SCRIPT enter "$name" in response to "thecommand" instead of having the user manually input it themselves?
you can add input by pipe like this:
echo yourname | ./yourscript
for more inputs you can use printf
printf "input1\ninput2" | ./yourscript
where \n means new line and it will be used like new input.
Run your script like:
./yourscript.sh < file.txt
where file.txt will contain the name.
now your script will look for name from the file(file.txt), in file.txt you can type the names which will act as input for read command.
read command reads on line at a time so if u have more than on read command in your script you should have multiple lines in file.txt file
For complicated cases, for example if your input depends on the output of your command, you may write an "expect" script.
To see how it works you can auto-generate such script interactively
$ autoexpect thecommand
And then run it
$ expect -f script.exp
I want to write several lines (5 or more) to a file I'm going to create in script. I can do this by echo >> filename. But I would like to know what the best way to do this?
You can use a here document:
cat <<EOF >> outputfile
some lines
of text
EOF
I usually use the so-called "here-document" Dennis suggested. An alternative is:
(echo first line; echo second line) >> outputfile
This should have comparable performance in bash, as (....) starts a subshell, but echo is 'inlined' - bash does not run /bin/echo, but does the echo by itself.
It might even be faster because it involves no exec().
This style is even more useful if you want to use output from another command somewhere in the text.
I'm trying to automate a proces which I have to do over and over again in which I have to parse the output from a shell function, look for 5 different things, and then put them on a file
I know I can match patterns with grep however I don't know how to store the result on a variable so I can use it after :(
I also have to parse this very same output to get the other 5 values
I have no idea on how to use the same output for the 5 grep's i need to do and then store it to 5 different variables for after use
I know i have to create a nice and tidy .sh but I don't know how to do this
Currently im trying this
#!/bin/bash
data=$(cat file)
lol=$(echo data|grep red)
echo $lol
not working , any ideas?
you should show some examples of what you want to do next time..
assuming you shell function is called func1
func1(){
echo "things i want to get are here"
}
func1 | grep -E "things|want|are|here|get" > outputfile.txt
Update:
your code
#!/bin/bash
data=$(cat file)
lol=$(echo data|grep red)
echo $lol
practically just means this
lol=$(grep "red" file)
or
lol=$(awk '/red/' file)
also, if you are considering using bash, this is one way you can do it
while read -r myline
do
case "$myline" in
*"red"* ) echo "$myline" >> output.txt
esac
done <file
You can use the following syntax:
VAR=$(grep foo bar)
or alternatively:
VAR=`grep foo bar`
The easiest thing to do would be to redirect the output of the function to a file. You can then run multiple greps on it and only delete the file once you are done with it.
To save the output, you want to use command substitution. This runs a command and then converts the output into command line parameter. Combined with variable assignment you get:
variable=$(grep expression file)
Your second line is wrong. Change it to this:
lol=$(echo "$data"|grep red)
use egrep istead of grep.
variable=$(egrep "exp1|exp2|exp3|exp4|exp5" file)