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Annotation of 43BSDTahoe/new/help/src/cshell/aliases, revision 1.1

1.1     ! root        1: .TI CSHELL/ALIASES
        !             2: Renaming and Abbreviating Commands [DRAFT]
        !             3: 
        !             4: 
        !             5: Aliases provide a means of setting up a name of your choosing
        !             6: to refer to a command or sequence of commands.
        !             7: When you use that name as if it were a command,
        !             8: the C shell replaces it with the command sequence to which it refers.
        !             9: Aliases effectively allow you to abbreviate commands
        !            10: and to alter the meaning of existing commands,
        !            11: although only from your point of view.
        !            12: 
        !            13: You set up an alias with the alias command
        !            14: 
        !            15:        \fBalias\fP \fIname\fP \fItext\fP
        !            16: 
        !            17: where \fIname\fP is the name you choose and \fItext\fP
        !            18: is the replacing text of the command or commands to which
        !            19: \fIname\fP will refer.
        !            20: For example, the aliases
        !            21: .IP
        !            22: .nf
        !            23: % alias pe printenv
        !            24: % alias nr nroff -ms -Tdtc -s1
        !            25: .LP
        !            26: would cause the shell to replace your subsequent command "pe"
        !            27: with "printenv" before executing it, and similarly for "nr".
        !            28: The actual replacements are shown below for two sample commands.
        !            29: The first command is what causes the shell to print the result
        !            30: of the replacement just before executing it.
        !            31: .IP
        !            32: .nf
        !            33: % set echo
        !            34: % pe TERM
        !            35: printenv TERM
        !            36: % nr chap1 chap2 > out
        !            37: nroff -ms -Tdtc -s1 chap1 chap2 > out
        !            38: .LP
        !            39: Notice that when you use an alias, whatever you entered on the rest
        !            40: of the line stays on the end after the replacement.
        !            41: This will not be the case when special alias arguments are used,
        !            42: but that is explained later.
        !            43: 
        !            44: One of the trickiest parts about aliases is quoting.
        !            45: For instance the quotes in
        !            46: .IP
        !            47: % alias doit 'tbl chap1 chap2 | nroff -ms -Tlpr | lpr'
        !            48: .LP
        !            49: are needed because without them the shell would have
        !            50: perceived three command instead of one.
        !            51: The following alias lists the files on the hypothetical
        !            52: gumball machine after printing the name of the remote directory first;
        !            53: it has more subtle quoting problems:
        !            54: .IP
        !            55: % alias rlist 'rsh gumball "echo $cwd ; ls" | more'
        !            56: .LP
        !            57: The outermost quotes achieve the same effect as in the
        !            58: previous example, and they have to differ from the
        !            59: inner quotes to be interpreted correctly.
        !            60: Unfortunately, the variable $cwd will always be replaced with
        !            61: the current directory on the local machine because the
        !            62: C shell insists on doing variable
        !            63: substitution within enclosing " marks.
        !            64: Thus even inverting the use of " and ' above would not work.
        !            65: Several acceptable ways are
        !            66: .IP
        !            67: .nf
        !            68: % alias rlist "rsh gumball 'echo" '$cwd' "; ls' | more"
        !            69: % alias rlist 'rsh gumball echo \\$cwd \\; ls | more'
        !            70: % alias rlist rsh gumball echo \\\\\\$cwd \\\\\\; ls \\| more'
        !            71: .LP
        !            72: and no one can say which one is best.
        !            73: 
        !            74: Since it is possible to choose an alias name that is currently
        !            75: the name of a normal system command, you can effectively replace or
        !            76: remove a system command.
        !            77: For example,
        !            78: .IP
        !            79: .nf
        !            80: % alias rm echo Sorry, cannot remove
        !            81: % rm thesis
        !            82: Sorry, cannot remove thesis
        !            83: % alias troff /usr/old/troff
        !            84: .LP
        !            85: You may want to know the aliases currently in effect,
        !            86: and can always find out by entering the alias command with
        !            87: no argument.
        !            88: If you enter it with one argument, the shell prints the
        !            89: the replacing text for the argument, if any.
        !            90: 
        !            91: There is also room for deviant or whimsical uses of aliases.
        !            92: .IP
        !            93: .nf
        !            94: % alias why echo BECAUSE
        !            95: % why
        !            96: BECAUSE
        !            97: % alias vi x
        !            98: % alias x y
        !            99: % alias y echo Bus error -- core dumped
        !           100: % vi myfile
        !           101: Bus error -- core dumped myfile
        !           102: % alias a alias
        !           103: % a
        !           104: a      alias
        !           105: vi     x
        !           106: why    (echo BECAUSE)
        !           107: x      y
        !           108: y      (echo Bus error -- core dumped)
        !           109: .LP
        !           110: Aliases can also work like simple, fast shell scripts with arguments;
        !           111: simple because only one-line commands work, and fast because 
        !           112: no new process is involved and no extra file has to be accessed
        !           113: (as with the source command).
        !           114: Unfortunately, the mechanism for accessing arguments
        !           115: involves complicated history-like
        !           116: substitutions and difficult quoting problems.
        !           117: 
        !           118: When you use an alias, any arguments you give to it
        !           119: are usually tacked on to the end of the replacing text when
        !           120: the shell does the replacement.
        !           121: This practice is suspended completely if your replacing
        !           122: text contains what appear to be history substitutions.
        !           123: Instead, the C shell selectively places the arguments
        !           124: into the replacing text based on the history constructs
        !           125: you used to define the alias.
        !           126: 
        !           127: Here is how it works.
        !           128: When the shell replaces the command you typed in with the text
        !           129: of the alias, it treats your original command as if it were the
        !           130: very last command.
        !           131: Thus, for example, !$ inside the definition
        !           132: of your alias would be replaced by the last argument with which
        !           133: the alias was invoked.
        !           134: In the alias
        !           135: .IP
        !           136: .nf
        !           137: % alias whois 'grep \\!:1 /etc/passwd \\!:2*'
        !           138: % set echo
        !           139: % whois fred > junk
        !           140: grep fred /etc/passwd > junk
        !           141: .LP
        !           142: the \\!:1 designates the first argument and \\!:2* designates
        !           143: all the rest.
        !           144: Remember that nothing but \\ will quote !.
        !           145: Here is an alias which lets you do arithmetic in the C shell:
        !           146: .IP
        !           147: .nf
        !           148: % alias val '@ z = (\\!*) ; echo $z'
        !           149: % val 3 - 2 * 6
        !           150: -9
        !           151: .LP
        !           152: Although aliases have many interesting properties,
        !           153: you may find them difficult to use and easy to get along without.
        !           154: On that note, here are some aliases that might appear
        !           155: in a real .cshrc file, which can set up aliases for you
        !           156: automatically when you login.
        !           157: 
        !           158: .nf
        !           159: alias h history -r +20
        !           160: alias j jobs -l
        !           161: alias m more
        !           162: alias q exit
        !           163: alias z suspend
        !           164: set whoami = `hostname | sed s/ucb//`
        !           165: alias cd 'chdir \\!* ; set prompt = "$whoami $cwd:t % "'
        !           166: cd
        !           167: alias la 'set q=$whoami ; if (\\!$ != la) set q=\\!$ ; ruptime | fgrep $q'
        !           168: alias ll ls -l
        !           169: alias lld ls -ld
        !           170: alias pd 'pushd \\!:* ; set prompt = "$whoami $cwd:t % "'
        !           171: alias pe printenv
        !           172: alias so source
        !           173: alias ts 'set noglob ; eval `tset -s \\!*`';
        !           174: alias pop 'popd \\!:* ; set prompt = "$whoami $cwd:t % "'
        !           175: alias grab 'sed "/^From: .*\\!:1/,/^From/\\\\!d" /usr/spool/mail/jak \\!:2*'
        !           176: alias whois 'grep \\!:1 /etc/passwd \\!:2*'
        !           177: alias alarm 'set mail = (5 \\!* $mail)'
        !           178: alias hic 'if ($i == $whoami) continue ; echo $i'
        !           179: alias ismail '@ q = 1 + (-z /usr/spool/mail/\\!^) + (-e /usr/spool/mail/\\!^) ; \\
        !           180:                set s = ("No mail file" Yep Nope) ; echo $s[$q]'
        !           181: alias slpr "sed 's/^/          /' \\!* | lpr"
        !           182: alias val "echo 'scale=5 ; \\!*:x' | bc"
        !           183: alias Troff troff -Q -Tcat
        !           184: alias Vroff troff -Q -Tversatec
        !           185: alias Iroff troff -Q -T6670
        !           186: 
        !           187: 
        !           188: jak

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