Ubuntu – ‘bash’ command in bash

bashcommand line

I just typed bash in Ubuntu's terminal and, it was like normal. But after that, I had to type exit twice. What is bash command in bash?

Best Answer

There is a difference between shells and terminal emulators.

Shell is a thing that passes your commands to the kernel, and that is executed. And terminal emulator programs let you interact with the shell. Examples of Terminal emualtors are gnome-terminal,konsole and shells are bash,zsh,sh etc. Terminal emulators are simply named as Terminal in most desktop environments.

When you open Terminal, it uses a shell by default. For most terminals it is bash. You can change the default shell. First run whoami to get your user name. Then run cat /etc/passwd | grep user_name where user_name is your user name. The last word is your default shell. Now you can change your shell with sudo usermod --shell /bin/shell_name user_name.

Also when you type bash it just opens another shell. You can simply exit the other shell by running exit. Such as executing zsh or sh will take you to other shell. You can read the man pages of shell with man shell_name to learn the differences between shells. However the man pages are extremely large and complicated to read that it will make your head spin. Executing a man shell_name | wc -l will give you the line count.

Hope that helps

Related Solutions

Ubuntu – How to get long command lines to wrap to the next line

Make sure all non-printable bytes in your PS1 are contained within \[ \]. Otherwise, bash will count them in the length of the prompt. It uses the length of the prompt to determine when to wrap the line.

For example, here bash counts the prompt as 19 columns wide, while the prompt displayed by the terminal is only 10 columns wide (My prompt written in cyan, and > written in default color):

PS1='\e[36mMy prompt\e[0m>'         # bash count: 19, actual: 10

while here it only counts the prompt as 10 columns wide because it ignores the bytes between the special \[ and \] escapes:

PS1='\[\e[36m\]My prompt\[\e[0m\]>' # bash count: 10, actual: 10

For good practice though, use tput to generate the terminal escapes rather than hard coding them:

cyan=$(tput setaf 6) # \e[36m
reset=$(tput sgr0)   # \e[0m
PS1='\[$cyan\]My prompt\[$reset\]>'

See http://mywiki.wooledge.org/BashFAQ/053, and also http://wiki.bash-hackers.org/scripting/terminalcodes for more on tput.

Ubuntu – How to find the version of bash I am running

The -v parameter for bash stands for verbose, and instructs bash to print out as much information as possible about what it is doing. On startup, it will print out all the configuration it is reading in.

To print out the version information for bash, use bash --version.

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Related Solutions

Ubuntu – How to get long command lines to wrap to the next line

Ubuntu – How to find the version of bash I am running

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