$(command) is “command substitution”. As you seem to understand, it runs the command, captures its output, and inserts that into the command line that contains the $(…); e.g., $ ls -ld $(date +%B).txt -rwxr-xr-x 1 Noob Noob 867 Jul 2 11:09 July.txt ${parameter} is “parameter substitution”. A lot of information can be found in the shell’s man page, bash (1), under the “ Parameter ...
Shell - "Shell" is a program, which facilitates the interaction between the user and the operating system (kernel). There are many shell implementations available, like sh, Bash, C shell, Z shell, etc.
The shell will try to create directory test and then, only if it was successful will try create file inside it. So you may interrupt a sequence of steps if one of them failed.
I often come across $?, $0, $1, $2, etc in shell scripting. I know that $? returns the exit status of the last command: echo "this will return 0" echo $? But what do the others do? What ...
I understand the basic difference between an interactive shell and a non-interactive shell. But what exactly differentiates a login shell from a non-login shell? Can you give examples for uses of...
The shell is the program which actually processes commands and returns output. Most shells also manage foreground and background processes, command history and command line editing.
Special shell variables verbose If set, causes the words of each command to be printed, after history substitution (if any). Set by the -v command line option. echo If set, each command with its arguments is echoed just before it is executed. For non-builtin commands all expansions occur before echoing.
docker debug <container or image> It allows you to get a shell (bash/fish/zsh) into any container. It also works for stopped containers and images. Essentially it's a replacement of docker exec -it <container> sh but with more features and less constraints (eg the debug shell has an install command to add further tools).
