I am trying to make a loop that will loop until the escape key is pressed but I have a struggle with printing the read message because if any key, except the enter key, it will continue to print in one line
Here is my code:
while : ; do
read -n1 -r -p "Press esc key to continue...\n" key
[[ $key != $'\e' ]] || break
done
It outputs Press esc key to continue...\n
You can use $'...' string like you're using for detecting escape character already:
while : ; do
read -n1 -r -p $'Press esc key to continue...\n' key
[[ $key != $'\e' ]] || break
done
As per man bash:
Words of the form $'string' are treated specially. The word expands to string, with backslash-escaped characters replaced as specified by the ANSI C
standard. Backslash escape sequences are \n, \t, \e etc.
I'd restructure just a little bit!
1.) The input message ("Press esc key to continue...") shouldn't have an embedded newline. This newline, I'm assuming, should appear after the user presses escape.
1a.) We also don't want user input popping up on the screen, so read -s (silently) after echoing -n (no newline) your input prompt.
Original:
read -n1 -r -p "Press esc key to continue...\n" key
Modified:
echo -n "Press esc key to continue..."; read -s -n1 -r key
2.) Now, when the user presses ESC, I believe you'd like to initiate a newline & exit the loop, so just echo AND break on the ESC key press. Boom.
2a.) On the issue of everything BUT an escape re-printing the message...Well, let's do a carriage return if the user DOESN'T hit escape, that way the message is printed in the same spot instead of on a new line!
Original:
[[ $key != $'\e' ]] || break
Modified:
if [[ $key == $'\e' ]];then echo;break; else echo -ne "\033[0K\r"; fi
Finished version:
while : ; do
echo -n "Press esc key to continue..."; read -s -n1 -r key
if [[ $key == $'\e' ]];then echo;break; else echo -ne "\033[0K\r"; fi
done
Testing it (a bunch of random NON-ESCAPE keys):
Let me know if that works for you!
I need to read a value from the terminal in a bash script. I would like to be able to provide a default value that the user can change.
# Please enter your name: Ricardo^
In this script the prompt is "Please enter your name: " the default value is "Ricardo" and the cursor would be after the default value. Is there a way to do this in a bash script?
You can use parameter expansion, e.g.
read -p "Enter your name [Richard]: " name
name=${name:-Richard}
echo $name
Including the default value in the prompt between brackets is a fairly common convention
What does the :-Richard part do? From the bash manual:
${parameter:-word}
If parameter is unset or null, the expansion of word is substituted. Otherwise, the value of parameter is substituted.
Also worth noting that...
In each of the cases below, word is subject to tilde expansion, parameter expansion, command substitution, and arithmetic expansion.
So if you use webpath=${webpath:-~/httpdocs} you will get a result of /home/user/expanded/path/httpdocs not ~/httpdocs, etc.
read -e -p "Enter Your Name:" -i "Ricardo" NAME
echo $NAME
Notes:
This option requires bash 4 or higher (bash --version)
On macos, install current bash using homebrew - brew.sh
-e and -i work together: -e uses readline, -i inserts text using readline
bash 4+ manual page for read - linuxcommand.org
In Bash 4:
name="Ricardo"
read -e -i "$name" -p "Please enter your name: " input
name="${input:-$name}"
This displays the name after the prompt like this:
Please enter your name: Ricardo
with the cursor at the end of the name and allows the user to edit it. The last line is optional and forces the name to be the original default if the user erases the input or default (submitting a null).
Code:
IN_PATH_DEFAULT="/tmp/input.txt"
read -p "Please enter IN_PATH [$IN_PATH_DEFAULT]: " IN_PATH
IN_PATH="${IN_PATH:-$IN_PATH_DEFAULT}"
OUT_PATH_DEFAULT="/tmp/output.txt"
read -p "Please enter OUT_PATH [$OUT_PATH_DEFAULT]: " OUT_PATH
OUT_PATH="${OUT_PATH:-$OUT_PATH_DEFAULT}"
echo "Input: $IN_PATH Output: $OUT_PATH"
Sample run:
Please enter IN_PATH [/tmp/input.txt]:
Please enter OUT_PATH [/tmp/output.txt]: ~/out.txt
Input: /tmp/input.txt Output: ~/out.txt
I found this question, looking for a way to present something like:
Something interesting happened. Proceed [Y/n/q]:
Using the above examples I deduced this:-
echo -n "Something interesting happened. "
DEFAULT="y"
read -e -p "Proceed [Y/n/q]:" PROCEED
# adopt the default, if 'enter' given
PROCEED="${PROCEED:-${DEFAULT}}"
# change to lower case to simplify following if
PROCEED="${PROCEED,,}"
# condition for specific letter
if [ "${PROCEED}" == "q" ] ; then
echo "Quitting"
exit
# condition for non specific letter (ie anything other than q/y)
# if you want to have the active 'y' code in the last section
elif [ "${PROCEED}" != "y" ] ; then
echo "Not Proceeding"
else
echo "Proceeding"
# do proceeding code in here
fi
Hope that helps someone to not have to think out the logic, if they encounter the same problem
I've just used this pattern, which I prefer:
read name || name='(nobody)'
name=Ricardo
echo "Please enter your name: $name \c"
read newname
[ -n "$newname" ] && name=$newname
Set the default; print it; read a new value; if there is a new value, use it in place of the default. There is (or was) some variations between shells and systems on how to suppress a newline at the end of a prompt. The '\c' notation seems to work on MacOS X 10.6.3 with a 3.x bash, and works on most variants of Unix derived from System V, using Bourne or Korn shells.
Also note that the user would probably not realize what is going on behind the scenes; their new data would be entered after the name already on the screen. It might be better to format it:
echo "Please enter your name ($name): \c"
#Script for calculating various values in MB
echo "Please enter some input: "
read input_variable
echo $input_variable | awk '{ foo = $1 / 1024 / 1024 ; print foo "MB" }'
The -e and -t parameter does not work together. i tried some expressions and the result was the following code snippet :
QMESSAGE="SHOULD I DO YES OR NO"
YMESSAGE="I DO"
NMESSAGE="I DO NOT"
FMESSAGE="PLEASE ENTER Y or N"
COUNTDOWN=2
DEFAULTVALUE=n
#----------------------------------------------------------------#
function REQUEST ()
{
read -n1 -t$COUNTDOWN -p "$QMESSAGE ? Y/N " INPUT
INPUT=${INPUT:-$DEFAULTVALUE}
if [ "$INPUT" = "y" -o "$INPUT" = "Y" ] ;then
echo -e "\n$YMESSAGE\n"
#COMMANDEXECUTION
elif [ "$INPUT" = "n" -o "$INPUT" = "N" ] ;then
echo -e "\n$NMESSAGE\n"
#COMMANDEXECUTION
else
echo -e "\n$FMESSAGE\n"
REQUEST
fi
}
REQUEST
I have an old shell script which needs to be moved to bash. This script prints progress of some activity and waits for user's commands. If no action is taken by user for 15 seconds screen is redrawn with new progress and timer starts again. Here's my problem:
I am trying to use read -t 15 myVar - this way after 15 seconds of waiting loop will be restarted. There is however a scenario which brings me a problem:
screen redrawn and script waits for input (prints 'Enter command:')
user enters foo but doesn't press enter
after 15 seconds screen is again redrawn and script waits for input - note, that foo is not displayed anywhere on the screen (prints 'Enter command:')
user enters bar and presses enter
At this moment variable $myVar holds 'foobar'.
What do I need? I am looking for a way to find the first string typed by user, so I could redisplay it after refreshing status. This way user will see:
Enter command: foo
On Solaris I could use stty -pendin to save input into some sort of a buffer, and after refresh run stty pendin to get this input from buffer and print it on a screen.
Is there a Linux equivalent to stty pendin feature? Or maybe you know some bash solution to my problem?
I guess one way would be to manually accumulate the user input ... use read with -n1 so that it returns after every character, then you can add it to your string. To prevent excessive drawing you would have to calculate how many remaining seconds are on the 15 second clock ...
Addendum:
For your comment about space/return - you basically want to use an IFS without the characters you want, such as space
example:
XIFS="${IFS}" # backup IFS
IFS=$'\r' # use a character your user is not likely to enter (or just the same but w/o the space)
# Enter will look like en empty string
$ read -n1 X; echo --; echo -n "${X}" | od -tx1
--
0000000
# space will be presented as a character
$ read -n1 X; echo --; echo -n "${X}" | od -tx1
--
0000000 20
0000001
# after you are all done, you probably wantto restore the IFS
IFS="${XIFS}"
Expanding on what #nhed was saying, perhaps something like this:
#!/bin/bash
limit=5
draw_screen () {
clear;
echo "Elapsed time: $SECONDS" # simulate progress indicator
printf 'Enter command: %s' "$1"
}
increment=$limit
str=
end=0
while ! [ $end -eq 1 ] ; do
draw_screen "$str"
while [ $SECONDS -lt $limit ] && [ $end -eq 0 ] ; do
c=
IFS= read -t $limit -r -n 1 -d '' c
if [ "$c" = $'\n' ] ; then
end=1
fi
str="${str}${c}"
done
let limit+=increment
done
str="${str%$'\n'}" # strip trailing newline
echo "input was: '$str'"
The solution is not ideal:
You can sometimes be typing in the middle of the loop and mess up input
You can't edit anything nicely (but this is fixable with a lot more work)
But maybe it's enough for you.
If you have Bash 4:
read -p 'Enter something here: ' -r -t 15 -e -i "$myVar" myVar
The -e turns on readline support for the user's text entry. The -i uses the following text as the default contents of the input buffer which it displays to the user. The following text in this case is the previous contents of the variable you're reading into.
Demonstration:
$ myVar='this is some text' # simulate previous entry
$ read -p 'Enter something here: ' -r -t 15 -e -i "$myVar" myVar
Enter something here: this is some text[]
Where [] represents the cursor. The user will be able to backspace and correct the previous text, if needed.
OK, I think I have the solution. I took nhed's proposition and worked a bit on it :)
The main code prints some status and waits for input:
while :
do
# print the progress on the screen
echo -n "Enter command: "
tput sc # save the cursor position
echo -n "$tmpBuffer" # this is buffer which holds typed text (no 'ENTER' key yet)
waitForUserInput
read arguments <<< $(echo $mainBuffer) # this buffer is set when user presses 'ENTER'
mainBuffer="" # don't forget to clear it after reading
# now do the action requested in $arguments
done
Function waitForUserInput waits 10 seconds for a keypress. If nothing typed - exits, but already entered keys are saved in a buffer. If key is pressed, it is parsed (added to buffer, or removed from buffer in case of backspace). On Enter buffer is saved to another buffer, from which it is read for further processing:
function waitForUserInput {
saveIFS=$IFS # save current IFS
IFS="" # change IFS to empty string, so 'ENTER' key can be read
while :
do
read -t10 -n1 char
if (( $? == 0 ))
then
# user pressed something, so parse it
case $char in
$'\b')
# remove last char from string with sed or perl
# move cursor to saved position with 'tput rc'
echo -n "$tmpBuffer"
;;
"")
# empty string is 'ENTER'
# so copy tmpBuffer to mainBuffer
# clear tmpBuffer and return to main loop
IFS=$saveIFS
return 0
;;
*)
# any other char - add it to buffer
tmpBuffer=$tmpBuffer$char
;;
esac
else
# timeout occured, so return to main function
IFS=$saveIFS
return 1
fi
done
}
Thanks to all of you for your help!
I have bash script like the following:
#!/bin/bash
echo "Please enter your username";
read username;
echo "Please enter your password";
read password;
I want that when the user types the password on the terminal, it should not be displayed (or something like *******) should be displayed). How do I achieve this?
Just supply -s to your read call like so:
$ read -s PASSWORD
$ echo $PASSWORD
Update
In case you want to get fancy by outputting an * for each character they type, you can do something like this (using andreas' read -s solution):
unset password;
while IFS= read -r -s -n1 pass; do
if [[ -z $pass ]]; then
echo
break
else
echo -n '*'
password+=$pass
fi
done
Without being fancy
echo "Please enter your username";
read username;
echo "Please enter your password";
stty -echo
read password;
stty echo
you can use stty to disable echo
this solution works without bash or certain features from read
stty_orig=$(stty -g)
stty -echo
read password
stty $stty_orig
If you use this in a shell script then also set an exit handler which restores echo:
#! /bin/sh
stty_orig=$(stty -g)
trap "stty ${stty_orig}" EXIT
stty -echo
...
this is to make sure echo is restored regardless of how the script exits. otherwise the echo will stay off if the script errors out.
to turn echo back on manually type the following command
stty echo
you will have to type blindly because you do not see what you type.
i suggest to press ctrl+c first to clear anything else you might have typed before.
trivia
echo means to echo your typed input back to your screen.
this is from the time we worked on teletypewriters (that is what the tty means). a teletypewriter is like a typewriter but connected to another teletypewriter or computer. typically via telephone cable.
the workflow on a teletypewriter is roughly as follows: you type in your command (or message for the other side). then the teletypewriter will print the response from the other side.
when you work on a teletypewriter you see your input as you type. this is because the teletypewriter is also a typewriter and as such prints the characters as you press them.
when teletypewriters where replaced by screens there was no longer a typewriter which types your input. instead we had to deliberate code an "echo" function which prints your input as you type.
i do not know whether stty -echo also disabled printing on a teletypewriter.
see here for a teletypewriter in action: https://www.youtube.com/watch?v=2XLZ4Z8LpEE (first part is restoration. action starting at about 12 minutes in)
more teletypewriter restoration: https://www.youtube.com/playlist?list=PL-_93BVApb5-9eQLTCk9xx16RAGEYHH1q
Here's a variation on #SiegeX's excellent *-printing solution for bash with support for backspace added; this allows the user to correct their entry with the backspace key (delete key on a Mac), as is typically supported by password prompts:
#!/usr/bin/env bash
password=''
while IFS= read -r -s -n1 char; do
[[ -z $char ]] && { printf '\n' >/dev/tty; break; } # ENTER pressed; output \n and break.
if [[ $char == $'\x7f' ]]; then # backspace was pressed
# Remove last char from output variable.
[[ -n $password ]] && password=${password%?}
# Erase '*' to the left.
printf '\b \b' >/dev/tty
else
# Add typed char to output variable.
password+=$char
# Print '*' in its stead.
printf '*' >/dev/tty
fi
done
Note:
As for why pressing backspace records character code 0x7f: "In modern systems, the backspace key is often mapped to the delete character (0x7f in ASCII or Unicode)" https://en.wikipedia.org/wiki/Backspace
\b \b is needed to give the appearance of deleting the character to the left; just using \b moves the cursor to the left, but leaves the character intact (nondestructive backspace). By printing a space and moving back again, the character appears to have been erased (thanks, The "backspace" escape character '\b': unexpected behavior?).
In a POSIX-only shell (e.g., sh on Debian and Ubuntu, where sh is dash), use the stty -echo approach (which is suboptimal, because it prints nothing), because the read builtin will not support the -s and -n options.
A bit different from (but mostly like) #lesmana's answer
stty -echo
read password
stty echo
simply: hide echo
do your stuff
show echo
I always like to use Ansi escape characters:
echo -e "Enter your password: \x1B[8m"
echo -e "\x1B[0m"
8m makes text invisible and 0m resets text to "normal." The -e makes Ansi escapes possible.
The only caveat is that you can still copy and paste the text that is there, so you probably shouldn't use this if you really want security.
It just lets people not look at your passwords when you type them in. Just don't leave your computer on afterwards. :)
NOTE:
The above is platform independent as long as it supports Ansi escape sequences.
However, for another Unix solution, you could simply tell read to not echo the characters...
printf "password: "
let pass $(read -s)
printf "\nhey everyone, the password the user just entered is $pass\n"
Here is a variation of #SiegeX's answer which works with traditional Bourne shell (which has no support for += assignments).
password=''
while IFS= read -r -s -n1 pass; do
if [ -z "$pass" ]; then
echo
break
else
printf '*'
password="$password$pass"
fi
done
Get Username and password
Make it more clear to read but put it on a better position over the screen
#!/bin/bash
clear
echo
echo
echo
counter=0
unset username
prompt=" Enter Username:"
while IFS= read -p "$prompt" -r -s -n 1 char
do
if [[ $char == $'\0' ]]; then
break
elif [ $char == $'\x08' ] && [ $counter -gt 0 ]; then
prompt=$'\b \b'
username="${username%?}"
counter=$((counter-1))
elif [ $char == $'\x08' ] && [ $counter -lt 1 ]; then
prompt=''
continue
else
counter=$((counter+1))
prompt="$char"
username+="$char"
fi
done
echo
unset password
prompt=" Enter Password:"
while IFS= read -p "$prompt" -r -s -n 1 char
do
if [[ $char == $'\0' ]]; then
break
elif [ $char == $'\x08' ] && [ $counter -gt 0 ]; then
prompt=$'\b \b'
password="${password%?}"
counter=$((counter-1))
elif [ $char == $'\x08' ] && [ $counter -lt 1 ]; then
echo
prompt=" Enter Password:"
continue
else
counter=$((counter+1))
prompt='*'
password+="$char"
fi
done
A variation on both #SiegeX and #mklement0's excellent contributions: mask user input; handle backspacing; but only backspace for the length of what the user has input (so we're not wiping out other characters on the same line) and handle control characters, etc... This solution was found here after so much digging!
#!/bin/bash
#
# Read and echo a password, echoing responsive 'stars' for input characters
# Also handles: backspaces, deleted and ^U (kill-line) control-chars
#
unset PWORD
PWORD=
echo -n 'password: ' 1>&2
while true; do
IFS= read -r -N1 -s char
# Note a NULL will return a empty string
# Convert users key press to hexadecimal character code
code=$(printf '%02x' "'$char") # EOL (empty char) -> 00
case "$code" in
''|0a|0d) break ;; # Exit EOF, Linefeed or Return
08|7f) # backspace or delete
if [ -n "$PWORD" ]; then
PWORD="$( echo "$PWORD" | sed 's/.$//' )"
echo -n $'\b \b' 1>&2
fi
;;
15) # ^U or kill line
echo -n "$PWORD" | sed 's/./\cH \cH/g' >&2
PWORD=''
;;
[01]?) ;; # Ignore ALL other control characters
*) PWORD="$PWORD$char"
echo -n '*' 1>&2
;;
esac
done
echo
echo $PWORD
I want to pause input in a shell script, and prompt the user for choices.
The standard Yes, No, or Cancel type question.
How do I accomplish this in a typical bash prompt?
The simplest and most widely available method to get user input at a shell prompt is the read command. The best way to illustrate its use is a simple demonstration:
while true; do
read -p "Do you wish to install this program? " yn
case $yn in
[Yy]* ) make install; break;;
[Nn]* ) exit;;
* ) echo "Please answer yes or no.";;
esac
done
Another method, pointed out by Steven Huwig, is Bash's select command. Here is the same example using select:
echo "Do you wish to install this program?"
select yn in "Yes" "No"; do
case $yn in
Yes ) make install; break;;
No ) exit;;
esac
done
With select you don't need to sanitize the input – it displays the available choices, and you type a number corresponding to your choice. It also loops automatically, so there's no need for a while true loop to retry if they give invalid input.
Also, Léa Gris demonstrated a way to make the request language agnostic in her answer. Adapting my first example to better serve multiple languages might look like this:
set -- $(locale LC_MESSAGES)
yesexpr="$1"; noexpr="$2"; yesword="$3"; noword="$4"
while true; do
read -p "Install (${yesword} / ${noword})? " yn
if [[ "$yn" =~ $yesexpr ]]; then make install; exit; fi
if [[ "$yn" =~ $noexpr ]]; then exit; fi
echo "Answer ${yesword} / ${noword}."
done
Obviously other communication strings remain untranslated here (Install, Answer) which would need to be addressed in a more fully completed translation, but even a partial translation would be helpful in many cases.
Finally, please check out the excellent answer by F. Hauri.
At least five answers for one generic question.
Depending on
posix compliant: could work on poor systems with generic shell environments
bash specific: using so called bashisms
and if you want
simple ``in line'' question / answer (generic solutions)
pretty formatted interfaces, like ncurses or more graphical using libgtk or libqt...
use powerful readline history capability
1. POSIX generic solutions
You could use the read command, followed by if ... then ... else:
printf 'Is this a good question (y/n)? '
read answer
# if echo "$answer" | grep -iq "^y" ;then
if [ "$answer" != "${answer#[Yy]}" ] ;then # this grammar (the #[] operator) means that the variable $answer where any Y or y in 1st position will be dropped if they exist.
echo Yes
else
echo No
fi
(Thanks to Adam Katz's comment: Replaced the test above with one that is more portable and avoids one fork:)
POSIX, but single key feature
But if you don't want the user to have to hit Return, you could write:
(Edited: As #JonathanLeffler rightly suggest, saving stty's configuration could be better than simply force them to sane.)
printf 'Is this a good question (y/n)? '
old_stty_cfg=$(stty -g)
stty raw -echo ; answer=$(head -c 1) ; stty $old_stty_cfg # Careful playing with stty
if [ "$answer" != "${answer#[Yy]}" ];then
echo Yes
else
echo No
fi
Note: This was tested under sh, bash, ksh, dash and busybox!
Same, but waiting explicitly for y or n:
#/bin/sh
printf 'Is this a good question (y/n)? '
old_stty_cfg=$(stty -g)
stty raw -echo
answer=$( while ! head -c 1 | grep -i '[ny]' ;do true ;done )
stty $old_stty_cfg
if [ "$answer" != "${answer#[Yy]}" ];then
echo Yes
else
echo No
fi
Using dedicated tools
There are many tools which were built using libncurses, libgtk, libqt or other graphical libraries. For example, using whiptail:
if whiptail --yesno "Is this a good question" 20 60 ;then
echo Yes
else
echo No
fi
Depending on your system, you may need to replace whiptail with another similiar tool:
dialog --yesno "Is this a good question" 20 60 && echo Yes
gdialog --yesno "Is this a good question" 20 60 && echo Yes
kdialog --yesno "Is this a good question" 20 60 && echo Yes
where 20 is height of dialog box in number of lines and 60 is width of the dialog box. These tools all have near same syntax.
DIALOG=whiptail
if [ -x /usr/bin/gdialog ] ;then DIALOG=gdialog ; fi
if [ -x /usr/bin/xdialog ] ;then DIALOG=xdialog ; fi
...
$DIALOG --yesno ...
2. Bash specific solutions
Basic in line method
read -p "Is this a good question (y/n)? " answer
case ${answer:0:1} in
y|Y )
echo Yes
;;
* )
echo No
;;
esac
I prefer to use case so I could even test for yes | ja | si | oui if needed...
in line with single key feature
Under bash, we can specify the length of intended input for for the read command:
read -n 1 -p "Is this a good question (y/n)? " answer
Under bash, read command accepts a timeout parameter, which could be useful.
read -t 3 -n 1 -p "Is this a good question (Y/n)? " answer
[ -z "$answer" ] && answer="Yes" # if 'yes' have to be default choice
Timeout with countdown:
i=6 ;while ((i-->1)) &&
! read -sn 1 -t 1 -p $'\rIs this a good question (Y/n)? '$i$'..\e[3D' answer;do
:;done ;[[ $answer == [nN] ]] && answer=No || answer=Yes ;echo "$answer "
3. Some tricks for dedicated tools
More sophisticated dialog boxes, beyond simple yes - no purposes:
dialog --menu "Is this a good question" 20 60 12 y Yes n No m Maybe
Progress bar:
dialog --gauge "Filling the tank" 20 60 0 < <(
for i in {1..100};do
printf "XXX\n%d\n%(%a %b %T)T progress: %d\nXXX\n" $i -1 $i
sleep .033
done
)
Little demo:
#!/bin/sh
while true ;do
[ -x "$(which ${DIALOG%% *})" ] || DIALOG=dialog
DIALOG=$($DIALOG --menu "Which tool for next run?" 20 60 12 2>&1 \
whiptail "dialog boxes from shell scripts" >/dev/tty \
dialog "dialog boxes from shell with ncurses" \
gdialog "dialog boxes from shell with Gtk" \
kdialog "dialog boxes from shell with Kde" ) || break
clear;echo "Choosed: $DIALOG."
for i in `seq 1 100`;do
date +"`printf "XXX\n%d\n%%a %%b %%T progress: %d\nXXX\n" $i $i`"
sleep .0125
done | $DIALOG --gauge "Filling the tank" 20 60 0
$DIALOG --infobox "This is a simple info box\n\nNo action required" 20 60
sleep 3
if $DIALOG --yesno "Do you like this demo?" 20 60 ;then
AnsYesNo=Yes; else AnsYesNo=No; fi
AnsInput=$($DIALOG --inputbox "A text:" 20 60 "Text here..." 2>&1 >/dev/tty)
AnsPass=$($DIALOG --passwordbox "A secret:" 20 60 "First..." 2>&1 >/dev/tty)
$DIALOG --textbox /etc/motd 20 60
AnsCkLst=$($DIALOG --checklist "Check some..." 20 60 12 \
Correct "This demo is useful" off \
Fun "This demo is nice" off \
Strong "This demo is complex" on 2>&1 >/dev/tty)
AnsRadio=$($DIALOG --radiolist "I will:" 20 60 12 \
" -1" "Downgrade this answer" off \
" 0" "Not do anything" on \
" +1" "Upgrade this anser" off 2>&1 >/dev/tty)
out="Your answers:\nLike: $AnsYesNo\nInput: $AnsInput\nSecret: $AnsPass"
$DIALOG --msgbox "$out\nAttribs: $AnsCkLst\nNote: $AnsRadio" 20 60
done
More samples? Have a look at Using whiptail for choosing USB device and USB removable storage selector: USBKeyChooser
5. Using readline's history
Example:
#!/bin/bash
set -i
HISTFILE=~/.myscript.history
history -c
history -r
myread() {
read -e -p '> ' $1
history -s ${!1}
}
trap 'history -a;exit' 0 1 2 3 6
while myread line;do
case ${line%% *} in
exit ) break ;;
* ) echo "Doing something with '$line'" ;;
esac
done
This will create a file .myscript.history in your $HOME directory, than you could use readline's history commands, like Up, Down, Ctrl+r and others.
echo "Please enter some input: "
read input_variable
echo "You entered: $input_variable"
You can use the built-in read command ; Use the -p option to prompt the user with a question.
Since BASH4, you can now use -i to suggest an answer :
read -e -p "Enter the path to the file: " -i "/usr/local/etc/" FILEPATH
echo $FILEPATH
(But remember to use the "readline" option -e to allow line editing with arrow keys)
If you want a "yes / no" logic, you can do something like this:
read -e -p "
List the content of your home dir ? [Y/n] " YN
[[ $YN == "y" || $YN == "Y" || $YN == "" ]] && ls -la ~/
Bash has select for this purpose. Here's how you would use it in a script:
select result in Yes No Cancel
do
echo $result
done
This is what it would look like to use:
$ bash examplescript.sh
1) Yes
2) No
3) Cancel
#? 1
Yes
#? 2
No
#? 3
Cancel
#?
read -p "Are you alright? (y/n) " RESP
if [ "$RESP" = "y" ]; then
echo "Glad to hear it"
else
echo "You need more bash programming"
fi
inquire () {
echo -n "$1 [y/n]? "
read answer
finish="-1"
while [ "$finish" = '-1' ]
do
finish="1"
if [ "$answer" = '' ];
then
answer=""
else
case $answer in
y | Y | yes | YES ) answer="y";;
n | N | no | NO ) answer="n";;
*) finish="-1";
echo -n 'Invalid response -- please reenter:';
read answer;;
esac
fi
done
}
... other stuff
inquire "Install now?"
...
Here's something I put together:
#!/bin/sh
promptyn () {
while true; do
read -p "$1 " yn
case $yn in
[Yy]* ) return 0;;
[Nn]* ) return 1;;
* ) echo "Please answer yes or no.";;
esac
done
}
if promptyn "is the sky blue?"; then
echo "yes"
else
echo "no"
fi
I'm a beginner, so take this with a grain of salt, but it seems to work.
You want:
Bash builtin commands (i.e. portable)
Check TTY
Default answer
Timeout
Colored question
Snippet
do_xxxx=y # In batch mode => Default is Yes
[[ -t 0 ]] && # If TTY => Prompt the question
read -n 1 -p $'\e[1;32m
Do xxxx? (Y/n)\e[0m ' do_xxxx # Store the answer in $do_xxxx
if [[ $do_xxxx =~ ^(y|Y|)$ ]] # Do if 'y' or 'Y' or empty
then
xxxx
fi
Explanations
[[ -t 0 ]] && read ... => Call command read if TTY
read -n 1 => Wait for one character
$'\e[1;32m ... \e[0m ' => Print in green
(green is fine because readable on both white/black backgrounds)
[[ $do_xxxx =~ ^(y|Y|)$ ]] => bash regex
Timeout => Default answer is No
do_xxxx=y
[[ -t 0 ]] && { # Timeout 5 seconds (read -t 5)
read -t 5 -n 1 -p $'\e[1;32m
Do xxxx? (Y/n)\e[0m ' do_xxxx || # read 'fails' on timeout
do_xxxx=n ; } # Timeout => answer No
if [[ $do_xxxx =~ ^(y|Y|)$ ]]
then
xxxx
fi
The easiest way to achieve this with the least number of lines is as follows:
read -p "<Your Friendly Message here> : y/n/cancel" CONDITION;
if [ "$CONDITION" == "y" ]; then
# do something here!
fi
The if is just an example: it is up to you how to handle this variable.
Use the read command:
echo Would you like to install? "(Y or N)"
read x
# now check if $x is "y"
if [ "$x" = "y" ]; then
# do something here!
fi
and then all of the other stuff you need
This solution reads a single character and calls a function on a yes response.
read -p "Are you sure? (y/n) " -n 1
echo
if [[ $REPLY =~ ^[Yy]$ ]]; then
do_something
fi
It is possible to handle a locale-aware "Yes / No choice" in a POSIX shell; by using the entries of the LC_MESSAGES locale category, witch provides ready-made RegEx patterns to match an input, and strings for localized Yes No.
#!/usr/bin/env sh
# Getting LC_MESSAGES values into variables
# shellcheck disable=SC2046 # Intended IFS splitting
IFS='
' set -- $(locale LC_MESSAGES)
yesexpr="$1"
noexpr="$2"
yesstr="$3"
nostr="$4"
messages_codeset="$5" # unused here, but kept as documentation
# Display Yes / No ? prompt into locale
echo "$yesstr / $nostr ?"
# Read answer
read -r yn
# Test answer
case "$yn" in
# match only work with the character class from the expression
${yesexpr##^}) echo "answer $yesstr" ;;
${noexpr##^}) echo "answer $nostr" ;;
esac
EDIT:
As #Urhixidur mentioned in his comment:
Unfortunately, POSIX only specifies the first two (yesexpr and noexpr). On Ubuntu 16, yesstr and nostr are empty.
See: https://www.ee.ryerson.ca/~courses/ele709/susv4/xrat/V4_xbd_chap07.html#tag_21_07_03_06
LC_MESSAGES
The yesstr and nostr locale keywords and the YESSTR and NOSTR langinfo items were formerly used to match user affirmative and negative responses. In POSIX.1-2008, the yesexpr, noexpr, YESEXPR, and NOEXPR extended regular expressions have replaced them. Applications should use the general locale-based messaging facilities to issue prompting messages which include sample desired responses.
Alternatively using locales the Bash way:
#!/usr/bin/env bash
IFS=$'\n' read -r -d '' yesexpr noexpr _ < <(locale LC_MESSAGES)
printf -v yes_or_no_regex "(%s)|(%s)" "$yesexpr" "$noexpr"
printf -v prompt $"Please answer Yes (%s) or No (%s): " "$yesexpr" "$noexpr"
declare -- answer=;
until [[ "$answer" =~ $yes_or_no_regex ]]; do
read -rp "$prompt" answer
done
if [[ -n "${BASH_REMATCH[1]}" ]]; then
echo $"You answered: Yes"
else
echo $"No, was your answer."
fi
The answer is matched using locale environment's provided regexps.
To translate the remaining messages, use bash --dump-po-strings scriptname to output the po strings for localization:
#: scriptname:8
msgid "Please answer Yes (%s) or No (%s): "
msgstr ""
#: scriptname:17
msgid "You answered: Yes"
msgstr ""
#: scriptname:19
msgid "No, was your answer."
msgstr ""
To get a nice ncurses-like inputbox use the command dialog like this:
#!/bin/bash
if (dialog --title "Message" --yesno "Want to do something risky?" 6 25)
# message box will have the size 25x6 characters
then
echo "Let's do something risky"
# do something risky
else
echo "Let's stay boring"
fi
The dialog package is installed by default at least with SUSE Linux. Looks like:
In my case I needed to read from a downloaded script i.e.,
curl -Ss https://example.com/installer.sh | sh
The line read -r yn </dev/tty allowed it to read input in this case.
printf "These files will be uploaded. Is this ok? (y/N) "
read -r yn </dev/tty
if [ "$yn" = "y" ]; then
# Yes
else
# No
fi
Single keypress only
Here's a longer, but reusable and modular approach:
Returns 0=yes and 1=no
No pressing enter required - just a single character
Can press enter to accept the default choice
Can disable default choice to force a selection
Works for both zsh and bash.
Defaulting to "no" when pressing enter
Note that the N is capitalsed. Here enter is pressed, accepting the default:
$ confirm "Show dangerous command" && echo "rm *"
Show dangerous command [y/N]?
Also note, that [y/N]? was automatically appended.
The default "no" is accepted, so nothing is echoed.
Re-prompt until a valid response is given:
$ confirm "Show dangerous command" && echo "rm *"
Show dangerous command [y/N]? X
Show dangerous command [y/N]? y
rm *
Defaulting to "yes" when pressing enter
Note that the Y is capitalised:
$ confirm_yes "Show dangerous command" && echo "rm *"
Show dangerous command [Y/n]?
rm *
Above, I just pressed enter, so the command ran.
No default on enter - require y or n
$ get_yes_keypress "Here you cannot press enter. Do you like this [y/n]? "
Here you cannot press enter. Do you like this [y/n]? k
Here you cannot press enter. Do you like this [y/n]?
Here you cannot press enter. Do you like this [y/n]? n
$ echo $?
1
Here, 1 or false was returned. Note that with this lower-level function you'll need to provide your own [y/n]? prompt.
Code
# Read a single char from /dev/tty, prompting with "$*"
# Note: pressing enter will return a null string. Perhaps a version terminated with X and then remove it in caller?
# See https://unix.stackexchange.com/a/367880/143394 for dealing with multi-byte, etc.
function get_keypress {
local REPLY IFS=
>/dev/tty printf '%s' "$*"
[[ $ZSH_VERSION ]] && read -rk1 # Use -u0 to read from STDIN
# See https://unix.stackexchange.com/q/383197/143394 regarding '\n' -> ''
[[ $BASH_VERSION ]] && </dev/tty read -rn1
printf '%s' "$REPLY"
}
# Get a y/n from the user, return yes=0, no=1 enter=$2
# Prompt using $1.
# If set, return $2 on pressing enter, useful for cancel or defualting
function get_yes_keypress {
local prompt="${1:-Are you sure [y/n]? }"
local enter_return=$2
local REPLY
# [[ ! $prompt ]] && prompt="[y/n]? "
while REPLY=$(get_keypress "$prompt"); do
[[ $REPLY ]] && printf '\n' # $REPLY blank if user presses enter
case "$REPLY" in
Y|y) return 0;;
N|n) return 1;;
'') [[ $enter_return ]] && return "$enter_return"
esac
done
}
# Credit: http://unix.stackexchange.com/a/14444/143394
# Prompt to confirm, defaulting to NO on <enter>
# Usage: confirm "Dangerous. Are you sure?" && rm *
function confirm {
local prompt="${*:-Are you sure} [y/N]? "
get_yes_keypress "$prompt" 1
}
# Prompt to confirm, defaulting to YES on <enter>
function confirm_yes {
local prompt="${*:-Are you sure} [Y/n]? "
get_yes_keypress "$prompt" 0
}
You can use the default REPLY on a read, convert to lowercase and compare to a set of variables with an expression.
The script also supports ja/si/oui
read -rp "Do you want a demo? [y/n/c] "
[[ ${REPLY,,} =~ ^(c|cancel)$ ]] && { echo "Selected Cancel"; exit 1; }
if [[ ${REPLY,,} =~ ^(y|yes|j|ja|s|si|o|oui)$ ]]; then
echo "Positive"
fi
read -e -p "Enter your choice: " choice
The -e option enables the user to edit the input using arrow keys.
If you want to use a suggestion as input:
read -e -i "yes" -p "Enter your choice: " choice
-i option prints a suggestive input.
Lots of good answers to this question, but from what I can see none of them are my ideal, which would:
Be simple, just a couple lines of shell
Work with a single y/n keypress (no need to press enter)
Default to yes if you just hit enter
Work with an uppercase Y/N as well
Here's my version which does has those properties:
read -n1 -p "Continue? (Y/n) " confirm
if ! echo $confirm | grep '^[Yy]\?$'; then
exit 1
fi
You can modify that conditional to only run on "yes" (just remove the ! in the if statement) or add an else if you want to run code on both branches.
One-liner:
read -p "Continue? [Enter] → Yes, [Ctrl]+[C] → No."
This assumes that "No" and "Cancel" have the same outcome, so no reason to treat them differently.
I noticed that no one posted an answer showing multi-line echo menu for such simple user input so here is my go at it:
#!/bin/bash
function ask_user() {
echo -e "
#~~~~~~~~~~~~#
| 1.) Yes |
| 2.) No |
| 3.) Quit |
#~~~~~~~~~~~~#\n"
read -e -p "Select 1: " choice
if [ "$choice" == "1" ]; then
do_something
elif [ "$choice" == "2" ]; then
do_something_else
elif [ "$choice" == "3" ]; then
clear && exit 0
else
echo "Please select 1, 2, or 3." && sleep 3
clear && ask_user
fi
}
ask_user
This method was posted in the hopes that someone may find it useful and time-saving.
Check this
read -p "Continue? (y/n): " confirm && [[ $confirm == [yY] || $confirm == [yY][eE][sS] ]] || exit 1
Multiple choice version:
ask () { # $1=question $2=options
# set REPLY
# options: x=..|y=..
while $(true); do
printf '%s [%s] ' "$1" "$2"
stty cbreak
REPLY=$(dd if=/dev/tty bs=1 count=1 2> /dev/null)
stty -cbreak
test "$REPLY" != "$(printf '\n')" && printf '\n'
(
IFS='|'
for o in $2; do
if [ "$REPLY" = "${o%%=*}" ]; then
printf '\n'
break
fi
done
) | grep ^ > /dev/null && return
done
}
Example:
$ ask 'continue?' 'y=yes|n=no|m=maybe'
continue? [y=yes|n=no|m=maybe] g
continue? [y=yes|n=no|m=maybe] k
continue? [y=yes|n=no|m=maybe] y
$
It will set REPLY to y (inside the script).
Inspired by the answers of #Mark and #Myrddin I created this function for a universal prompt
uniprompt(){
while true; do
echo -e "$1\c"
read opt
array=($2)
case "${array[#]}" in *"$opt"*) eval "$3=$opt";return 0;; esac
echo -e "$opt is not a correct value\n"
done
}
use it like this:
unipromtp "Select an option: (a)-Do one (x)->Do two (f)->Do three : " "a x f" selection
echo "$selection"
I suggest you use dialog...
Linux Apprentice: Improve Bash Shell Scripts Using Dialog
The dialog command enables the use of window boxes in shell scripts to make their use more interactive.
it's simple and easy to use, there's also a gnome version called gdialog that takes the exact same parameters, but shows it GUI style on X.
more generic would be:
function menu(){
title="Question time"
prompt="Select:"
options=("Yes" "No" "Maybe")
echo "$title"
PS3="$prompt"
select opt in "${options[#]}" "Quit/Cancel"; do
case "$REPLY" in
1 ) echo "You picked $opt which is option $REPLY";;
2 ) echo "You picked $opt which is option $REPLY";;
3 ) echo "You picked $opt which is option $REPLY";;
$(( ${#options[#]}+1 )) ) clear; echo "Goodbye!"; exit;;
*) echo "Invalid option. Try another one.";continue;;
esac
done
return
}
yn() {
if [[ 'y' == `read -s -n 1 -p "[y/n]: " Y; echo $Y` ]];
then eval $1;
else eval $2;
fi }
yn 'echo yes' 'echo no'
yn 'echo absent no function works too!'
One simple way to do this is with xargs -p or gnu parallel --interactive.
I like the behavior of xargs a little better for this because it executes each command immediately after the prompt like other interactive unix commands, rather than collecting the yesses to run at the end. (You can Ctrl-C after you get through the ones you wanted.)
e.g.,
echo *.xml | xargs -p -n 1 -J {} mv {} backup/
As a friend of a one line command I used the following:
while [ -z $prompt ]; do read -p "Continue (y/n)?" choice;case "$choice" in y|Y ) prompt=true; break;; n|N ) exit 0;; esac; done; prompt=;
Written longform, it works like this:
while [ -z $prompt ];
do read -p "Continue (y/n)?" choice;
case "$choice" in
y|Y ) prompt=true; break;;
n|N ) exit 0;;
esac;
done;
prompt=;
I've used the case statement a couple of times in such a scenario, using the case statment is a good way to go about it. A while loop, that ecapsulates the case block, that utilizes a boolean condition can be implemented in order to hold even more control of the program, and fulfill many other requirements. After the all the conditions have been met, a break can be used which will pass control back to the main part of the program. Also, to meet other conditions, of course conditional statements can be added to accompany the control structures: case statement and possible while loop.
Example of using a case statement to fulfill your request
#! /bin/sh
# For potential users of BSD, or other systems who do not
# have a bash binary located in /bin the script will be directed to
# a bourne-shell, e.g. /bin/sh
# NOTE: It would seem best for handling user entry errors or
# exceptions, to put the decision required by the input
# of the prompt in a case statement (case control structure),
echo Would you like us to perform the option: "(Y|N)"
read inPut
case $inPut in
# echoing a command encapsulated by
# backticks (``) executes the command
"Y") echo `Do something crazy`
;;
# depending on the scenario, execute the other option
# or leave as default
"N") echo `execute another option`
;;
esac
exit