How to display a list of shell variables?
Display a list of the shell environment variables or run a command with modified environment variables. env [OPTION]… [-] [NAME=VALUE]… COMMAND [ARG]… start with an empty environment. A mere – implies -i. remove variable from the environment before running the command. If no COMMAND, print the current environment variables. 4.12.3.
How to export a variable in a shell?
NAMEs are marked for automatic export to the environment of subsequently executed commands. export [name [=value] …] Existing variables may be exported. Variables may also exported as their value is assigned. Display a list of the shell environment variables or run a command with modified environment variables.
When to use a variable in a command in Bash?
Referencing the value of a variable Whenever Bash encounters a dollar-sign, immediately followed by a word, within a command or in a double-quoted string, it will attempt to replace that token with the value of the named variable. This is sometimes referred to as expanding the variable, or parameter substitution:
What does the variable$ # do in Unix?
The variable $# reports the number of command line arguments passed to the shell script program. Cause all of the positional parameters $2 to $n to be renamed $1 to $ (n-1), and $1 to be lost. Here is an example that just displays all of the command line arguments:
How to get a list of all variables in Bash?
For bash: (the standard shell in Ubuntu) Enter the following command in a terminal to print all the environment variables: printenv. For further information about this command, read the printenv man page. To show a list including the “shell variables” you can enter the next command: ( set -o posix ; set ) | less.
How to list all variables in Ubuntu command line?
printenv is an external command, so it only knows about (and prints) exported environment variables. set is an internal bash command, so it shows all the “shell variables” (unexported environment variables) as well as the exported environment variables.