Analysis of information sources in references of the Wikipedia article "PWB shell" in English language version.
In addition to these variables [$n, $p, $r, $s, and $t], the following is provided: $$ contains a 5-digit number that is the unique process number of the current shell. In some circumstances, it is necessary to know the number of a process, in order to kill it, for example. However, its most common use to date has been that of generating unique names for temporary files.
The "PWB Shell" first appeared in mid-1975. It derived from a set of requirements and suggestions from me in early 1975 in trying to do serious shell programming. In mid-1975, the shell acquired variables, including 3 that were derived from per-process data. This is where the idea of more generalised path- searching came in.
The original Thompson shell, the Mashey shell and the Bourne shell were all called sh, and they overlapped or replaced one another in the years 1970–1976 as they were refined and gained additional capabilities. ... The Thompson shell had no programming capabilities. This changed with the development of the Mashey shell (and later the Bourne shell).
In addition to these variables [$n, $p, $r, $s, and $t], the following is provided: $$ contains a 5-digit number that is the unique process number of the current shell. In some circumstances, it is necessary to know the number of a process, in order to kill it, for example. However, its most common use to date has been that of generating unique names for temporary files.
The original Thompson shell, the Mashey shell and the Bourne shell were all called sh, and they overlapped or replaced one another in the years 1970–1976 as they were refined and gained additional capabilities. ... The Thompson shell had no programming capabilities. This changed with the development of the Mashey shell (and later the Bourne shell).
The "PWB Shell" first appeared in mid-1975. It derived from a set of requirements and suggestions from me in early 1975 in trying to do serious shell programming. In mid-1975, the shell acquired variables, including 3 that were derived from per-process data. This is where the idea of more generalised path- searching came in.
