Bash Reference Manual For Bash Version 4 4

Here-strings in bash are implemented via temporary files, usually in the format /tmp/sh-thd., which are later unlinked, thus making them occupy some memory space temporarily but not show up in the list of /tmp directory entries, and effectively exist as anonymous files, which may still be referenced via file descriptor by the ...

Bash Reference Manual For Bash Version 4 4 1

In Bash, there appear to be several variables which hold special, consistently-meaning values. For instance, ./myprogram &; echo $! will return the PID of the process which backgrounded myprog...

bash - What are the special dollar sign shell variables ... - Stack ...

bash - What is the purpose of "&&" in a shell command? - Stack Overflow

If not quoted, it is a pattern match! (From the Bash man page: "Any part of the pattern may be quoted to force it to be matched as a string."). Here in Bash, the two statements yielding "yes" are pattern matching, other three are string equality:

Bash Reference Manual For Bash Version 4 4 5

What is the operator =~ called? I'm not sure it has a name. The bash documentation just calls it the =~ operator. Is it only used to compare the right side against the left side? The right side is considered an extended regular expression. If the left side matches, the operator returns 0, and 1 otherwise. Why are double square brackets required when running a test? Because =~ is an operator of ...

Bash Reference Manual For Bash Version 4 4 6

In Bash, when you hit enter, a fork + exec + wait happens like above, and bash then sets $? to the exit status of the forked process. Note: for built-in commands like echo, a process need not be spawned, and Bash just sets $? to 0 to simulate an external process.