UNIX FAQ Version 2.1 92/12/04

Below are the answers to some Frequently Asked Questions about UNIX. See also comp.unix.questions and comp.unix.shell.

These articles are divided approximately as follows:

1.*) General questions.
2.*) Relatively basic questions, likely to be asked by beginners.
3.*) Intermediate questions.
4.*) Advanced questions, likely to be asked by people who thought they already knew all of the answers.
5.*) Questions pertaining to the various shells, and the differences.
6.*) An overview of Unix variants.
7.*) An comparison of configuration management systems (RCS, SCCS).

General questions

1.1): Who helped you put this list together?
1.2): When someone refers to 'rn(1)' or 'ctime(3)', what does the number in parentheses mean?
1.3): What does {some strange unix command name} stand for?
1.4): How does the gateway between "comp.unix.questions" and the "info-unix" mailing list work?
1.5): What are some useful Unix or C books?
1.6): What happened to the pronunciation list that used to be part of this document?

2.1): How do I remove a file whose name begins with a "-" ?
2.2): How do I remove a file with funny characters in the filename ?
2.3): How do I get a recursive directory listing?
2.4): How do I get the current directory into my prompt?
2.5): How do I read characters from the terminal in a shell script?
2.6): How do I rename "*.foo" to "*.bar", or change file names to lowercase?
2.7): Why do I get [some strange error message] when I "rsh host command" ?
2.8): How do I {set an environment variable, change directory} inside a program or shell script and have that change affect my current shell?
2.9): How do I redirect stdout and stderr separately in csh?
2.10): How do I tell inside .cshrc if I'm a login shell?
2.11): How do I construct a shell glob-pattern that matches all files except "." and ".." ?
2.12): How do I find the last argument in a Bourne shell script?
2.13): What's wrong with having '.' in your $PATH ?

3.1): How do I find out the creation time of a file?
3.2): How do I use "rsh" without having the rsh hang around until the remote command has completed?
3.3): How do I truncate a file?
3.4): Why doesn't find's "{}" symbol do what I want?
3.5): How do I set the permissions on a symbolic link?
3.6): How do I "undelete" a file?
3.7): How can a process detect if it's running in the background?
3.8): Why doesn't redirecting a loop work as intended? (Bourne shell)
3.9): How do I run 'passwd', 'ftp', 'telnet', 'tip' and other interactive programs from a shell script or in the background?
3.10): How do I find out the process ID of a program with a particular name from inside a shell script or C program?
3.11): How do I check the exit status of a remote command executed via "rsh" ?
3.12): Is it possible to pass shell variable settings into an awk program?
3.13): How do I get rid of zombie processes that persevere?
3.14): How do I get lines from a pipe as they are written instead of only in larger blocks.

4.1): How do I read characters from a terminal without requiring the user to hit RETURN?
4.2): How do I check to see if there are characters to be read without actually reading?
4.3): How do I find the name of an open file?
4.4): How can an executing program determine its own pathname?
4.5): How do I use popen() to open a process for reading AND writing?
4.6): How do I sleep() in a C program for less than one second?
4.7): How can I get setuid shell scripts to work?
4.8): How can I find out which user or process has a file open or is using a particular file system (so that I can unmount it?)
4.9): How do I keep track of people who are fingering me?
4.10): Is it possible to reconnect a process to a terminal after it has been disconnected, e.g. after starting a program in the background and logging out?
4.11): Is it possible to "spy" on a terminal, displaying the output that's appearing on it on another terminal?

5.1): Can shells be classified into categories?
5.2): How do I "include" one shell script from within another shell script?
5.3): Do all shells have aliases? Is there something else that can be used?
5.4): How are shell variables assigned?
5.5): How can I tell if I am running an interactive shell?
5.6): What "dot" files do the various shells use?
5.7): I would like to know more about the differences between the various shells. Is this information available some place?