wall command in Linux system is used to write a message to all users. This command displays a message, or the contents of a file, or otherwise its standard input, on the terminals of all currently logged in users. The lines which will be longer than 79 characters, wrapped by this command. Short lines are whitespace padded to have 79 characters. A carriage return and newline at the end of each line is put by wall command always. Only the superuser can write on the terminals of users who have chosen to deny messages or are using a program which automatically denies messages. Reading from a file is refused when the invoker is not superuser and the program is suid(set-user-ID) or sgid(set-group-ID).
wall [-n] [-t timeout] [message | file]
- wall -n: This option will suppress the banner.
- wall -t: This option will abandon the write attempt to the terminals after timeout seconds. This timeout needs to be a positive integer. The by default value is 300 seconds, which is a legacy from the time when peoples ran terminals over modem lines.
wall -t 30
- wall -V : This option display version information and exit.
- wall -h : This option will display help message and exit.
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