CONTENTS

SYNOPSIS

DESCRIPTION

"Argument list processing"

The rest of the flag arguments are interpreted as follows:

Non-login shells read only /etc/csh.cshrc and ~/.tcshrc or ~/.cshrc on startup.

"The command-line editor (+)"

The shell always binds the arrow keys (as defined in the TERMCAP environment variable) to

unless doing so would alter another single-character binding. One can set the arrow key escape sequences to the empty string with settc to prevent these bindings. The ANSI/VT100 sequences for arrow keys are always bound.

Other key bindings are, for the most part, what Emacs and vi(1) users would expect and can easily be displayed by bindkey, so there is no need to list them here. Likewise, bindkey can list the editor commands with a short description of each.

Completion works anywhere in the line, not at just the end; completed text pushes the rest of the line to the right. Completion in the middle of a word often results in leftover characters to the right of the cursor that need to be deleted.

Commands and variables can be completed in much the same way. For example, typing ‘em[tab]’ would complete ‘em’ to ‘emacs’ if emacs were the only command on your system beginning with ‘em’. Completion can find a command in any directory in path or if given a full pathname. Typing ‘echo $ar[tab]’ would complete ‘$ar’ to ‘$argv’ if no other variable began with ‘ar’.

The shell parses the input buffer to determine whether the word you want to complete should be completed as a filename, command or variable. The first word in the buffer and the first word following ‘;’, ‘|’, ‘|&’, ‘&&’ or ‘||’ is considered to be a command. A word beginning with ‘$’ is considered to be a variable. Anything else is a filename. An empty line is ‘completed’ as a filename.

You can list the possible completions of a word at any time by typing ‘^D’ to run the delete-char-or-list-or-eof editor command. The shell lists the possible completions using the ls-F builtin (q.v.) and reprints the prompt and unfinished command line, for example:

A filename to be completed can contain variables, your own or others’ home directories abbreviated with ‘~’ (see Filename substitution) and directory stack entries abbreviated with ‘=’ (see Directory stack substitution). For example,

delete-char-or-list-or-eof lists at only the end of the line; in the middle of a line it deletes the character under the cursor and on an empty line it logs one out or, if ignoreeof is set, does nothing. ‘M-^D’, bound to the editor command list-choices, lists completion possibilities anywhere on a line, and list-choices (or any one of the related editor commands that do or don’t delete, list and/or log out, listed under delete-char-or-list-or-eof) can be bound to ‘^D’ with the bindkey builtin command if so desired.

The complete-word-fwd and complete-word-back editor commands (not bound to any keys by default) can be used to cycle up and down through the list of possible completions, replacing the current word with the next or previous word in the list.

The shell variable fignore can be set to a list of suffixes to be ignored by completion. Consider the following:

If the complete shell variable is set to ‘enhance’, completion 1) ignores case and 2) considers periods, hyphens and underscores (‘.’, ‘-’ and ‘_’) to be word separators and hyphens and underscores to be equivalent. If you had the following files

Completion and listing are affected by several other shell variables: recexact can be set to complete on the shortest possible unique match, even if more typing might result in a longer match:

Individual words can be spelling-corrected with the spell-word editor command (usually bound to M-s and M-S) and the entire input buffer with spell-line (usually bound to M-$). The correct shell variable can be set to ‘cmd’ to correct the command name or ‘all’ to correct the entire line each time return is typed, and autocorrect can be set to correct the word to be completed before each completion attempt.

When spelling correction is invoked in any of these ways and the shell thinks that any part of the command line is misspelled, it prompts with the corrected line:

Spelling correction recognizes user-defined completions (see the complete builtin command). If an input word in a position for which a completion is defined resembles a word in the completion list, spelling correction registers a misspelling and suggests the latter word as a correction. However, if the input word does not match any of the possible completions for that position, spelling correction does not register a misspelling.

Like completion, spelling correction works anywhere in the line, pushing the rest of the line to the right and possibly leaving extra characters to the right of the cursor.

The character or characters to which each command is bound by default is given in parentheses. ‘^character’ means a control character and ‘M-character’ a meta character, typed as escape-character on terminals without a meta key. Case counts, but commands that are bound to letters by default are bound to both lower- and uppercase letters for convenience.

"Lexical structure"

When the shell’s input is not a terminal, the character ‘#’ is taken to begin a comment. Each ‘#’ and the rest of the input line on which it appears is discarded before further parsing.

A special character (including a blank or tab) may be prevented from having its special meaning, and possibly made part of another word, by preceding it with a backslash (‘#146;) or enclosing it in single (‘’’), double (‘"’) or backward (‘‘’) quotes. When not otherwise quoted a newline preceded by a ‘#146; is equivalent to a blank, but inside quotes this sequence results in a newline.

"History substitution"

Saved commands are numbered sequentially from 1 and stamped with the time. It is not usually necessary to use event numbers, but the current event number can be made part of the prompt by placing an ‘!’ in the prompt shell variable.

The shell actually saves history in expanded and literal (unexpanded) forms. If the histlit shell variable is set, commands that display and store history use the literal form.

The history builtin command can print, store in a file, restore and clear the history list at any time, and the savehist and histfile shell variables can be can be set to store the history list automatically on logout and restore it on login.

History substitutions introduce words from the history list into the input stream, making it easy to repeat commands, repeat arguments of a previous command in the current command, or fix spelling mistakes in the previous command with little typing and a high degree of confidence.

History substitutions begin with the character ‘!’. They may begin anywhere in the input stream, but they do not nest. The ‘!’ may be preceded by a ‘#146; to prevent its special meaning; for convenience, a ‘!’ is passed unchanged when it is followed by a blank, tab, newline, ‘=’ or ‘(’. History substitutions also occur when an input line begins with ‘^’. This special abbreviation will be described later. The characters used to signal history substitution (‘!’ and ‘^’) can be changed by setting the histchars shell variable. Any input line which contains a history substitution is printed before it is executed.

A history substitution may have an ‘‘event specification’’, which indicates the event from which words are to be taken, a ‘‘word designator’’, which selects particular words from the chosen event, and/or a ‘‘modifier’’, which manipulates the selected words.

An event specification can be

For example, consider this bit of someone’s history list:

History references may be insulated from the surrounding text with braces if necessary. For example, ‘!vdoc’ would look for a command beginning with ‘vdoc’, and, in this example, not find one, but ‘!{v}doc’ would expand unambiguously to ‘vi wumpus.mandoc’. Even in braces, history substitutions do not nest.

(+) While csh(1) expands, for example, ‘!3d’ to event 3 with the letter ‘d’ appended to it, tcsh expands it to the last event beginning with ‘3d’; only completely numeric arguments are treated as event numbers. This makes it possible to recall events beginning with numbers. To expand ‘!3d’ as in csh(1) say ‘!\3d’.

To select words from an event we can follow the event specification by a ‘:’ and a designator for the desired words. The words of an input line are numbered from 0, the first (usually command) word being 0, the second word (first argument) being 1, etc. The basic word designators are:

Selected words are inserted into the command line separated by single blanks. For example, the ‘diff’ command in the previous example might have been typed as ‘diff !!:1.old !!:1’ (using ‘:1’ to select the first argument from the previous event) or ‘diff !-2:2 !-2:1’ to select and swap the arguments from the ‘cp’ command. If we didn’t care about the order of the ‘diff’ we might have said ‘diff !-2:1-2’ or simply ‘diff !-2:*’. The ‘cp’ command might have been written ‘cp wumpus.man !#:1.old’, using ‘#’ to refer to the current event. ‘!n:- hurkle.man’ would reuse the first two words from the ‘nroff’ command to say ‘nroff -man hurkle.man’.

The ‘:’ separating the event specification from the word designator can be omitted if the argument selector begins with a ‘^’, ‘$’, ‘*’, ‘%’ or ‘-’. For example, our ‘diff’ command might have been ‘diff !!^.old !!^’ or, equivalently, ‘diff !!$.old !!$’. However, if ‘!!’ is abbreviated ‘!’, an argument selector beginning with ‘-’ will be interpreted as an event specification.

A history reference may have a word designator but no event specification. It then references the previous command. Continuing our ‘diff’ example, we could have said simply ‘diff !^.old !^’ or, to get the arguments in the opposite order, just ‘diff !*’.

The word or words in a history reference can be edited, or ‘‘modified’’, by following it with one or more modifiers, each preceded by a ‘:’:

Modifiers are applied to only the first modifiable word (unless ‘g’ is used). It is an error for no word to be modifiable.

For example, the ‘diff’ command might have been written as ‘diff wumpus.man.old !#^:r’, using ‘:r’ to remove ‘.old’ from the first argument on the same line (‘!#^’). We could say ‘echo hello out there’, then ‘echo !*:u’ to capitalize ‘hello’, ‘echo !*:au’ to say it out loud, or ‘echo !*:agu’ to really shout. We might follow ‘mail -s "I forgot my password" rot’ with ‘!:s/rot/root’ to correct the spelling of ‘root’ (but see Spelling correction for a different approach).

There is a special abbreviation for substitutions. ‘^’, when it is the first character on an input line, is equivalent to ‘!:s^’. Thus we might have said ‘^rot^root’ to make the spelling correction in the previous example. This is the only history substitution which does not explicitly begin with ‘!’.

(+) In csh as such, only one modifier may be applied to each history or variable expansion. In tcsh, more than one may be used, for example

(+) Variables may be made read-only with ‘set -r’ (q.v.) Read-only variables may not be modified or unset; attempting to do so will cause an error. Once made read-only, a variable cannot be made writable, so ‘set -r’ should be used with caution. Environment variables cannot be made read-only.

Some variables are set by the shell or referred to by it. For instance, the argv variable is an image of the shell’s argument list, and words of this variable’s value are referred to in special ways. Some of the variables referred to by the shell are toggles; the shell does not care what their value is, only whether they are set or not. For instance, the verbose variable is a toggle which causes command input to be echoed. The -v command line option sets this variable. Special shell variables lists all variables which are referred to by the shell.

Other operations treat variables numerically. The ‘@’ command permits numeric calculations to be performed and the result assigned to a variable. Variable values are, however, always represented as (zero or more) strings. For the purposes of numeric operations, the null string is considered to be zero, and the second and subsequent words of multi-word values are ignored.

After the input line is aliased and parsed, and before each command is executed, variable substitution is performed keyed by ‘$’ characters. This expansion can be prevented by preceding the ‘$’ with a ‘\’ except within ‘"’s where it always occurs, and within ‘’’s where it never occurs. Strings quoted by ‘‘’ are interpreted later (see Command substitution below) so ‘$’ substitution does not occur there until later, if at all. A ‘$’ is passed unchanged if followed by a blank, tab, or end-of-line.

Input/output redirections are recognized before variable expansion, and are variable expanded separately. Otherwise, the command name and entire argument list are expanded together. It is thus possible for the first (command) word (to this point) to generate more than one word, the first of which becomes the command name, and the rest of which become arguments.

Unless enclosed in ‘"’ or given the ‘:q’ modifier the results of variable substitution may eventually be command and filename substituted. Within ‘"’, a variable whose value consists of multiple words expands to a (portion of a) single word, with the words of the variable’s value separated by blanks. When the ‘:q’ modifier is applied to a substitution the variable will expand to multiple words with each word separated by a blank and quoted to prevent later command or filename substitution.

The following metasequences are provided for introducing variable values into the shell input. Except as noted, it is an error to reference a variable which is not set.

$name

"Command, filename and directory stack substitution"

"Command substitution"

Command substitutions inside double quotes (‘"’) retain blanks and tabs; only newlines force new words. The single final newline does not force a new word in any case. It is thus possible for a command substitution to yield only part of a word, even if the command outputs a complete line.

In matching filenames, the character ‘.’ at the beginning of a filename or immediately following a ‘/’, as well as the character ‘/’ must be matched explicitly. The character ‘*’ matches any string of characters, including the null string. The character ‘?’ matches any single character. The sequence ‘[...]’ matches any one of the characters enclosed. Within ‘[...]’, a pair of characters separated by ‘-’ matches any character lexically between the two.

(+) Some glob-patterns can be negated: The sequence ‘[^...]’ matches any single character not specified by the characters and/or ranges of characters in the braces.

An entire glob-pattern can also be negated with ‘^’:

The metanotation ‘a{b,c,d}e’ is a shorthand for ‘abe ace ade’. Left-to-right order is preserved: ‘/usr/source/s1/{oldls,ls}.c’ expands to ‘/usr/source/s1/oldls.c /usr/source/s1/ls.c’. The results of matches are sorted separately at a low level to preserve this order: ‘../{memo,*box}’ might expand to ‘../memo ../box ../mbox’. (Note that ‘memo’ was not sorted with the results of matching ‘*box’.) It is not an error when this construct expands to files which do not exist, but it is possible to get an error from a command to which the expanded list is passed. This construct may be nested. As a special case the words ‘{’, ‘}’ and ‘{}’ are passed undisturbed.

The character ‘~’ at the beginning of a filename refers to home directories. Standing alone, i.e., ‘~’, it expands to the invoker’s home directory as reflected in the value of the home shell variable. When followed by a name consisting of letters, digits and ‘-’ characters the shell searches for a user with that name and substitutes their home directory; thus ‘~ken’ might expand to ‘/usr/ken’ and ‘~ken/chmach’ to ‘/usr/ken/chmach’. If the character ‘~’ is followed by a character other than a letter or ‘/’ or appears elsewhere than at the beginning of a word, it is left undisturbed. A command like ‘setenv MANPATH /usr/man:/usr/local/man:~/lib/man’ does not, therefore, do home directory substitution as one might hope.

It is an error for a glob-pattern containing ‘*’, ‘?’, ‘[’ or ‘~’, with or without ‘^’, not to match any files. However, only one pattern in a list of glob-patterns must match a file (so that, e.g., ‘rm *.a *.c *.o’ would fail only if there were no files in the current directory ending in ‘.a’, ‘.c’, or ‘.o’), and if the nonomatch shell variable is set a pattern (or list of patterns) which matches nothing is left unchanged rather than causing an error.

The character ‘=’ followed by one or more digits expands to an entry in the directory stack. The special case ‘=-’ expands to the last directory in the stack. For example,

"Other substitutions (+)"

Commands

Simple commands, pipelines and sequences

Simple commands and pipelines may be joined into sequences with ‘;’, and will be executed sequentially. Commands and pipelines can also be joined into sequences with ‘||’ or ‘&&’, indicating, as in the C language, that the second is to be executed only if the first fails or succeeds respectively.

Parenthesized commands are always executed in a subshell.

When a command to be executed is found not to be a builtin command the shell attempts to execute the command via execve(2). Each word in the variable path names a directory in which the shell will look for the command. If it is given neither a -c nor a -t option, the shell hashes the names in these directories into an internal table so that it will try an execve(2) in only a directory where there is a possibility that the command resides there. This greatly speeds command location when a large number of directories are present in the search path. If this mechanism has been turned off (via unhash), if the shell was given a -c or -t argument or in any case for each directory component of path which does not begin with a ‘/’, the shell concatenates the current working directory with the given command name to form a path name of a file which it then attempts to execute.

If the file has execute permissions but is not an executable to the system (i.e., it is neither an executable binary nor a script that specifies its interpreter), then it is assumed to be a file containing shell commands and a new shell is spawned to read it. The shell special alias may be set to specify an interpreter other than the shell itself.

"Control flow"

The foreach, switch, and while statements, as well as the if-then-else form of the if statement, require that the major keywords appear in a single simple command on an input line as shown below.

"Logical, arithmetical and comparison operators"

"File inquiry operators"

file is command and filename expanded and then tested to see if it has the specified relationship to the real user. If file does not exist or is inaccessible or, for the operators indicated by ‘*’, if the specified file type does not exist on the current system, then all enquiries return false, i.e., ‘0’.

These operators may be combined for conciseness: ‘-xy file’ is equivalent to ‘-x file && -y file’. (+) For example, ‘-fx’ is true (returns ‘1’) for plain executable files, but not for directories.

L may be used in a multiple-operator test to apply subsequent operators to a symbolic link rather than to the file to which the link points. For example, ‘-lLo’ is true for links owned by the invoking user. Lr, Lw and Lx are always true for links and false for non-links. L has a different meaning when it is the last operator in a multiple-operator test; see below.

It is possible but not useful, and sometimes misleading, to combine operators which expect file to be a file with operators which do not, (e.g., X and t). Following L with a non-file operator can lead to particularly strange results.

Other operators return other information, i.e., not just ‘0’ or ‘1’. (+) They have the same format as before; op may be one of

Only one of these operators may appear in a multiple-operator test, and it must be the last. Note that L has a different meaning at the end of and elsewhere in a multiple-operator test. Because ‘0’ is a valid return value for many of these operators, they do not return ‘0’ when they fail: most return ‘-1’, and F returns ‘:’.

If the shell is compiled with POSIX defined (see the version shell variable), the result of a file inquiry is based on the permission bits of the file and not on the result of the access(2) system call. For example, if one tests a file with -w whose permissions would ordinarily allow writing but which is on a file system mounted read-only, the test will succeed in a POSIX shell but fail in a non-POSIX shell.

If you are running a job and wish to do something else you may hit the suspend key (usually ‘^Z’), which sends a STOP signal to the current job. The shell will then normally indicate that the job has been ‘Suspended’ and print another prompt. If the listjobs shell variable is set, all jobs will be listed like the jobs builtin command; if it is set to ‘long’ the listing will be in long format, like ‘jobs -l’. You can then manipulate the state of the suspended job. You can put it in the ‘‘background’’ with the bg command or run some other commands and eventually bring the job back into the ‘‘foreground’’ with fg. (See also the run-fg-editor editor command.) A ‘^Z’ takes effect immediately and is like an interrupt in that pending output and unread input are discarded when it is typed. The wait builtin command causes the shell to wait for all background jobs to complete.

The ‘^]’ key sends a delayed suspend signal, which does not generate a STOP signal until a program attempts to read(2) it, to the current job. This can usefully be typed ahead when you have prepared some commands for a job which you wish to stop after it has read them. The ‘^Y’ key performs this function in csh(1); in tcsh, ‘^Y’ is an editing command. (+)

A job being run in the background stops if it tries to read from the terminal. Background jobs are normally allowed to produce output, but this can be disabled by giving the command ‘stty tostop’. If you set this tty option, then background jobs will stop when they try to produce output like they do when they try to read input.

There are several ways to refer to jobs in the shell. The character ‘%’ introduces a job name. If you wish to refer to job number 1, you can name it as ‘%1’. Just naming a job brings it to the foreground; thus ‘%1’ is a synonym for ‘fg %1’, bringing job 1 back into the foreground. Similarly, saying ‘%1 &’ resumes job 1 in the background, just like ‘bg %1’. A job can also be named by an unambiguous prefix of the string typed in to start it: ‘%ex’ would normally restart a suspended ex(1) job, if there were only one suspended job whose name began with the string ‘ex’. It is also possible to say ‘%?string’ to specify a job whose text contains string, if there is only one such job.

The shell maintains a notion of the current and previous jobs. In output pertaining to jobs, the current job is marked with a ‘+’ and the previous job with a ‘-’. The abbreviations ‘%+’, ‘%’, and (by analogy with the syntax of the history mechanism) ‘%%’ all refer to the current job, and ‘%-’ refers to the previous job.

The sched builtin command puts commands in a scheduled-event list, to be executed by the shell at a given time.

The beepcmd, cwdcmd, periodic, precmd, postcmd, and jobcmd Special aliases can be set, respectively, to execute commands when the shell wants to ring the bell, when the working directory changes, every tperiod minutes, before each prompt, before each command gets executed, after each command gets executed, and when a job is started or is brought into the foreground.

The autologout shell variable can be set to log out or lock the shell after a given number of minutes of inactivity.

The mail shell variable can be set to check for new mail periodically.

The printexitvalue shell variable can be set to print the exit status of commands which exit with a status other than zero.

The rmstar shell variable can be set to ask the user, when ‘rm *’ is typed, if that is really what was meant.

The time shell variable can be set to execute the time builtin command after the completion of any process that takes more than a given number of CPU seconds.

When using the system’s NLS, the setlocale(3) function is called to determine appropriate character code/classification and sorting (e.g., a ’en_CA.UTF-8’ would yield "UTF-8" as a character code). This function typically examines the LANG and LC_CTYPE environment variables; refer to the system documentation for further details. When not using the system’s NLS, the shell simulates it by assuming that the ISO 8859-1 character set is used whenever either of the LANG and LC_CTYPE variables are set, regardless of their values. Sorting is not affected for the simulated NLS.

In addition, with both real and simulated NLS, all printable characters in the range \200-\377, i.e., those that have M-char bindings, are automatically rebound to self-insert-command. The corresponding binding for the escape-char sequence, if any, is left alone. These characters are not rebound if the NOREBIND environment variable is set. This may be useful for the simulated NLS or a primitive real NLS which assumes full ISO 8859-1. Otherwise, all M-char bindings in the range \240-\377 are effectively undone. Explicitly rebinding the relevant keys with bindkey is of course still possible.

On systems that support TCF (aix-ibm370, aix-ps2), getspath and setspath get and set the system execution path, getxvers and setxvers get and set the experimental version prefix and migrate migrates processes between sites. The jobs builtin prints the site on which each job is executing.

Under BS2000, bs2cmd executes commands of the underlying BS2000/OSD operating system.

Under Domain/OS, inlib adds shared libraries to the current environment, rootnode changes the rootnode and ver changes the systype.

Under Mach, setpath is equivalent to Mach’s setpath(1).

Under Masscomp/RTU and Harris CX/UX, universe sets the universe.

Under Harris CX/UX, ucb or att runs a command under the specified universe.

Under Convex/OS, warp prints or sets the universe.

The VENDOR, OSTYPE and MACHTYPE environment variables indicate respectively the vendor, operating system and machine type (microprocessor class or machine model) of the system on which the shell thinks it is running. These are particularly useful when sharing one’s home directory between several types of machines; one can, for example,

The version shell variable indicates what options were chosen when the shell was compiled.

In shell scripts, the shell’s handling of interrupt and terminate signals can be controlled with onintr, and its handling of hangups can be controlled with hup and nohup.

The echotc, settc and telltc commands can be used to manipulate and debug terminal capabilities from the command line.

"Builtin commands"

default:

"Special aliases (+)"

"Special shell variables"

The shell sets addsuffix, argv, autologout, csubstnonl, command, echo_style, edit, gid, group, home, loginsh, oid, path, prompt, prompt2, prompt3, shell, shlvl, tcsh, term, tty, uid, user and version at startup; they do not change thereafter unless changed by the user. The shell updates cwd, dirstack, owd and status when necessary, and sets logout on logout.

The shell synchronizes afsuser, group, home, path, shlvl, term and user with the environment variables of the same names: whenever the environment variable changes the shell changes the corresponding shell variable to match (unless the shell variable is read-only) and vice versa. Note that although cwd and PWD have identical meanings, they are not synchronized in this manner, and that the shell automatically interconverts the different formats of path and PATH.

ENVIRONMENT

FILES

"NEW FEATURES (+)"

A command-line editor, which supports GNU Emacs or vi(1)-style key bindings. See The command-line editor and Editor commands.

Programmable, interactive word completion and listing. See Completion and listing and the complete and uncomplete builtin commands.

Spelling correction (q.v.) of filenames, commands and variables.

Editor commands (q.v.) which perform other useful functions in the middle of typed commands, including documentation lookup (run-help), quick editor restarting (run-fg-editor) and command resolution (which-command).

An enhanced history mechanism. Events in the history list are time-stamped. See also the history command and its associated shell variables, the previously undocumented ‘#’ event specifier and new modifiers under History substitution, the *-history, history-search-*, i-search-*, vi-search-* and toggle-literal-history editor commands and the histlit shell variable.

Enhanced directory parsing and directory stack handling. See the cd, pushd, popd and dirs commands and their associated shell variables, the description of Directory stack substitution, the dirstack, owd and symlinks shell variables and the normalize-command and normalize-path editor commands.

Negation in glob-patterns. See Filename substitution.

New File inquiry operators (q.v.) and a filetest builtin which uses them.

A variety of Automatic, periodic and timed events (q.v.) including scheduled events, special aliases, automatic logout and terminal locking, command timing and watching for logins and logouts.

Shell builtin functions are not stoppable/restartable. Command sequences of the form ‘a ; b ; c’ are also not handled gracefully when stopping is attempted. If you suspend ‘b’, the shell will then immediately execute ‘c’. This is especially noticeable if this expansion results from an alias. It suffices to place the sequence of commands in ()’s to force it to a subshell, i.e., ‘( a ; b ; c )’.

Control over tty output after processes are started is primitive; perhaps this will inspire someone to work on a good virtual terminal interface. In a virtual terminal interface much more interesting things could be done with output control.

Alias substitution is most often used to clumsily simulate shell procedures; shell procedures should be provided rather than aliases.

Commands within loops are not placed in the history list. Control structures should be parsed rather than being recognized as built-in commands. This would allow control commands to be placed anywhere, to be combined with ‘|’, and to be used with ‘&’ and ‘;’ metasyntax.

foreach doesn’t ignore here documents when looking for its end.

It should be possible to use the ‘:’ modifiers on the output of command substitutions.

The screen update for lines longer than the screen width is very poor if the terminal cannot move the cursor up (i.e., terminal type ‘dumb’).

HPATH and NOREBIND don’t need to be environment variables.

Glob-patterns which do not use ‘?’, ‘*’ or ‘[]’ or which use ‘{}’ or ‘~’ are not negated correctly.

The single-command form of if does output redirection even if the expression is false and the command is not executed.

ls-F includes file identification characters when sorting filenames and does not handle control characters in filenames well. It cannot be interrupted.

Command substitution supports multiple commands and conditions, but not cycles or backward gotos.

TENEX was created at Bolt, Beranek & Newman (a Cambridge, Massachusetts think tank) in 1972 as an experiment in demand-paged virtual memory operating systems. They built a new pager for the DEC PDP-10 and created the OS to go with it. It was extremely successful in academia.

In 1975, DEC brought out a new model of the PDP-10, the KL10; they intended to have only a version of TENEX, which they had licensed from BBN, for the new box. They called their version TOPS-20 (their capitalization is trademarked). A lot of TOPS-10 users (‘The OPerating System for PDP-10’) objected; thus DEC found themselves supporting two incompatible systems on the same hardware--but then there were 6 on the PDP-11!

TENEX, and TOPS-20 to version 3, had command completion via a user-code-level subroutine library called ULTCMD. With version 3, DEC moved all that capability and more into the monitor (‘kernel’ for you Unix types), accessed by the COMND% JSYS (‘Jump to SYStem’ instruction, the supervisor call mechanism [are my IBM roots also showing?]).

The system limits argument lists to 10240 characters.

The number of arguments to a command which involves filename expansion is limited to 1/6th the number of characters allowed in an argument list.

Command substitutions may substitute no more characters than are allowed in an argument list.

VERSION

AUTHORS

"THANKS TO"