Editing Comparison of command shells (section)

=== Secure prompt ===
Some shell scripts need to query the user for sensitive information such as [[password]]s, private digital keys, [[Personal Identification Number|PIN codes]] or other confidential information. Sensitive input should not be echoed back to the screen/input device where it could be gleaned by unauthorized persons. Plaintext memory representation of sensitive information should also be avoided as it could allow the information to be compromised, e.g., through swap files, core dumps etc.<ref name="encryptmemory">{{cite web |author-last=Provos |author-first=Niels |title=Encrypting Virtual Memory |url=http://www.openbsd.org/papers/swapencrypt.ps |publisher=Center for Information Technology Integration, University of Michigan |access-date=2012-12-20}}</ref>

The shells bash, zsh and PowerShell offer this as a specific feature.<ref>{{cite web |url=https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html |title=bash - GNU Bourne-Again SHell |quote=read -s Silent mode. If input is coming from a terminal, characters are not echoed.}}</ref><ref>{{cite web |url=https://technet.microsoft.com/en-us/library/ee176935.aspx |title=Using the Read-Host Cmdlet |quote=By adding the -assecurestring parameter you can mask the data entered at the prompt}}</ref> Shells which do not offer this as a specific feature may still be able to turn off echoing through some other means. Shells executing on a Unix/Linux operating system can use the {{mono|[[stty]]}} external command to switch off/on echoing of input characters.<ref>{{cite web |title=Linux / Unix Command: stty |url=http://linux.about.com/od/commands/l/blcmdl1_stty.htm |publisher=Linux.about.com |access-date=2015-02-24 |archive-date=2015-02-25  |archive-url=https://web.archive.org/web/20150225005431/http://linux.about.com/od/commands/l/blcmdl1_stty.htm |url-status=dead }}</ref> In addition to not echoing back the characters, PowerShell's {{code|-AsSecureString}} option also encrypts the input character-by-character during the input process, ensuring that the string is never represented unencrypted in memory where it could be compromised through memory dumps, scanning, transcription etc.