Tcsh user manual

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In this chapter, I assume that you are in your home directory, and I refer to the startup files as. Your shell might also read system-wide startup files before reading the startup files in your home directory. System administrators sometimes use these files to standardize aspects of the working environment across accounts.

You can either leave those settings in place, or use commands like unset , unsetenv , unalias , and uncomplete to remove them. The generic versions might look something like this:. You may even decide to copy some of what you find into your own files. You can modify your working environment immediately by typing commands at the command line, but changes made that way disappear as soon as you log out. The changes take effect the next time you log in. Some guidelines for modifying your startup files are given below.

Before adding a command to a startup file, try it from the command line to make sure that it works. Make one change at a time. The shell treats lines that begin with as comments and ignores them. Use this feature to add comments that document your modifications. These comments will help you remember why you made your changes when you review your startup files later on. If you want to see what happens when a particular command is not executed, turn it into a comment by putting a in front of it.

If, later on, you want to undo the change, just remove the. After modifying a startup file, try it out. That way, if there is a problem, you find out immediately, but you still have your original login session running in your original environment , so that you can fix it. This is especially important if you introduce a serious error into a startup file that prevents further logins! Verify that you can log in successfully and that your changes have the desired effect.

If the shell seems to process only part of a startup file when you log in, be alert for error messages, and try to determine at what point in the execution of the file commands stop being processed. You will probably find a command with an error in it right before that point. Finally, as you gain experience modifying.

You can then use the source command to tell your current shell to reprocess it, rather than logging in again:. Variables control shell behavior, including the prompt display, where to look for commands, and whether to maintain a history list. The shell understands two kinds of variables: shell variables and environment variables. In general, shell variables are used internally by the shell and affect its own operation, whereas environment variables are accessible to programs started from the shell.

Appendix B , csh and tcsh Quick Reference , lists several useful variables of each type. Use the set command to define shell variables.

Some variables need no explicit value; they have an effect merely by existing:. Values that contain spaces or other special characters should be put in quotes, as in the set prompt command above. Values consisting of multiple strings must be surrounded with parentheses, as in the set fignore command.

If you do, there must be spaces on both sides:. I prefer to use spaces because I find set commands more readable that way. Environment variables differ from shell variables in that, although their values are known by the shell, those values are also accessible to programs you run from the shell. For example, if your mailer allows you to drop into an editor to edit a message, it might determine which editor to use by consulting the EDITOR environment variable.

Environment variable names are usually in uppercase type. Uppercase is not a requirement, but is a useful convention that helps distinguish environment variables from shell variables.

Use set or setenv with no argument to see the values of all your shell or environment variables:. Expands the variable to the left of the cursor. See Variable Substitution. Searches backwards through the history list for a command beginning with the current contents of the input buffer up to the cursor and copies it into the input buffer. Emacs mode only. See also history-search-forward and i-search-back. Searches backward like history-search-backward , copies the first match into the input buffer with the cursor positioned at the end of the pattern, and prompts with " bck: " and the first match.

Undoes the effect of the last character typed and deletes a character from the search pattern if appropriate. If the previous search was successful, aborts the entire search. If not, goes back to the last successful search. Inserts the last word of the previous input line "!

See also copy-prev-word. Lists completion possibilities as described under Completion and Listing. See also delete-char-or-list-or-eof and list-choices-raw. Lists via the ls-F builtin matches to the glob-pattern see Filename Substitution to the left of the cursor. Does list-choices or end-of-file on an empty line. Expands history substitutions in the current line, like expand-history , and inserts a space.

Searches for the current word in PATH and, if it's found, replaces it with the full path to the executable. Special characters are quoted.

Aliases are expanded and quoted but commands within aliases are not. This command is useful with commands that take commands as arguments, e. Expands the current word as described under the " expand " setting of the symlinks shell variable. This is used to toggle back and forth between an editor and the shell easily. Searches for documentation on the current command, using the same notion of "current command" as the completion routines, and prints it.

There is no way to use a pager; run-help is designed for short help files. If the special alias helpcommand is defined, it is run with the command name as a sole argument. Else, documentation should be in a file named command. If there is more than one help file only the first is printed. In insert mode the default , inserts the typed character into the input line after the character under the cursor.

In overwrite mode, replaces the character under the cursor with the typed character. The input mode is normally preserved between lines, but the inputmode shell variable can be set to " insert " or " overwrite " to put the editor in that mode at the beginning of each line. See also overwrite-mode. Indicates that the following characters are part of a multi-key sequence.

Binding a command to a multi-key sequence really creates two bindings: the first character to sequence-lead-in and the whole sequence to the command. All sequences beginning with a character bound to sequence-lead-in are effectively bound to undefined-key unless bound to another command. Attempts to correct the spelling of each word in the input buffer, like spell-word , but ignores words whose first character is one of " - ", "!

See Spelling correction. Attempts to correct the spelling of the current word as described under Spelling correction.

Checks each component of a word which appears to be a pathname. Expands or "unexpands" history substitutions in the input buffer. See also expand-history and the autoexpand shell variable. Copies the previous entry in the history list into the input buffer. If histlit is set, uses the literal form of the entry. May be repeated to step up through the history list, stopping at the top.

Prompts with "? The bell rings if no match is found. Hitting return ends the search and leaves the last match in the input buffer. Hitting escape ends the search and executes the match. Does a which see the description of the builtin command on the first word of the input buffer. When executed immediately after a yank or another yank-pop , replaces the yanked string with the next previous string from the killring. This also has the effect of rotating the killring, such that this string will be considered the most recently killed by a later yank command.

Repeating yank-pop will cycle through the killring any number of times. The current event. This should be used carefully in csh , where there is no check for recursion. The most recent event which contains the string s. The second? Remove a filename extension ". Substitute l for r. If l is empty "" , the l from a previous substitution or the s from a previous search or event number in event specification is used.

The trailing delimiter may be omitted if it's immediately followed by a newline. Apply the following modifier as many times as possible to a single word. Substitutes the words of the value of variable name , each separated by a blank.

Braces insulate nam e from following characters which would otherwise be part of it. Shell variables have names consisting of letters and digits starting with a letter. The underscore character is considered a letter. If name is not a shell variable, but is set in the environment, then that value is returned but some of the other forms given below are not available in this case. Substitutes only the selected words from the value of name.

The first word of a variable's value is numbered " 1 ". If the first number of a range is omitted it defaults to " 1 ".

It is not an error for a range to be empty if the second argument is omitted or in range. Substitutes the name of the file from which command input is being read. An error occurs if the name is not known. Substitutes " 1 " if the current input filename is known, " 0 " if it's not. Always " 0 " in interactive shells. Substitutes a line from the standard input , with no further interpretation after that.

It can read from the keyboard in a shell script. Furthermore, when tcsh is waiting for a line to be typed the user may type an interrupt to interrupt the sequence into which the line is to be substituted, but csh does not allow this. Open file name which is first variable, command and file name expanded as the standard input.

Read the shell input up to a line that is identical to word. Commands that are substituted have all blanks, tabs, and newlines preserved, except for the final newline that is dropped.

The resulting text is placed in an anonymous temporary file that is given to the command as standard input. The file name is used as standard output. If the file does not exist then it is created; if the file exists, it is truncated , its previous contents being lost. If the shell variable noclobber is set, then the file must not exist or be a character special file e. This helps prevent accidental destruction of files. In this case, the "! If the shell variable noclobber is set, then it is an error for the file not to exist, unless one of the "!

Executable in the path or shell builtin, e. The first form prints the values of all shell variables. The second form assigns the value of expr to name. The third form assigns the value of expr to the index 'th component of name ; both name and its index 'th component must already exist.

Note that the syntax of expr has nothing to do with that described under Expressions. The space between " " and name is required. Components of expr must be separated by spaces.

Without arguments, prints all aliases. With name , prints the alias for name. With name and wordlist , assigns wordlist as the alias of name. See also the unalias builtin command. Shows the amount of dynamic memory acquired, broken down into used and free memory. With an argument shows the number of free and used blocks in each size category.

The categories start at size 8 and double at each step. This command's output may vary across system types, because systems other than the VAX may use a different memory allocator. Puts the specified job s or, without arguments, the current job into the background, continuing each if it's stopped. Without options, the first form lists all bound keys and the editor command that each is bound, the second form lists the editor command that key is bound and the third form binds the editor command command to key.

Options include: -l. Lists or changes key-bindings in the alternative key map. This is the key map used in vi command mode. Removes key's binding. Be careful: " bindkey -r " does not bind key to self-insert-command , it unbinds key completely.

Bound keys in command are themselves reinterpreted, and this continues for ten levels of interpretation. Forces a break from option processing, so the next word is taken as key even if it begins with " - ". Passes bscommand to the BS command interpreter for execution. BS only. Causes execution to resume after the end of the nearest enclosing foreach or while.

The remaining commands on the current line are executed. Multi-level break s are thus possible by writing them all on one line. A synonym for the logout builtin command. Available only if the shell was so compiled; see the version shell variable. If a directory name is given, changes the shell's working directory to name.

If not, changes to home. If name is " - " it is interpreted as the previous working directory see Other Substitutions. With -p , prints the final directory stack, like dirs. The -l , -n and -v flags have the same effect on cd as on dirs , and they imply -p.

Using -- forces a break from option processing so the next word is taken as the directory name even if it begins with " - ". See also the implicitcd shell variable. Without arguments, lists all completions. With command , lists completions for command. With command and word etc. It can begin with " - " to indicate that completion should be used only when command is ambiguous.

Current-word completion. Next-word completion. Position-dependent completion. Continues execution of the nearest enclosing while or foreach. The rest of the commands on the current line are executed. The first form prints the directory stack. The top of the stack is at the left and the first directory in the stack is the current directory. With -n , entries are wrapped before they reach the edge of the screen. With -v , entries are printed one per line, preceded by their stack positions.

If more than one of -n or -v is given, -v takes precedence. With -S , the second form saves the directory stack to filename as a series of cd and pushd commands. With -L , the shell sources filename , which is presumably a directory stack file saved by the -S option or the savedirs mechanism. Note that login shells do the equivalent of " dirs -L " on startup and, if savedirs is set, " dirs -S " before exiting. The last form clears the directory stack. Writes each word to the shell's standard output, separated by spaces and terminated with a newline.

Exercises the terminal capabilities see termcap in args. For example, " echotc home " sends the cursor to the home position, " echotc cm 3 10 " sends it to column 3 and row 10, and " echotc ts 0; echo 'This is a test. If arg is " baud ", " cols ", " lines ", " meta " or " tabs ", prints the value of that capability " yes " or " no " indicating that the terminal does or does not have that capability.

With -v , messages are verbose. See the description of the foreach , if , switch , and while statements below. Treats the arguments as input to the shell and executes the resulting command s in the context of the current shell. Often executes commands generated as the result of command or variable substitution, because parsing occurs before these substitutions. See tset for a sample use of eval. The shell exits either with the value of the specified expr an expression, as described under Expressions or, without expr , with the value 0.

Brings the specified job s or, without arguments, the current job into the foreground, continuing each if it's stopped. Applies op which is a file inquiry operator as described under File inquiry operators to each file and returns the results as a space-separated list. Successively sets the variable name to each member of wordlist and executes the sequence of commands between this command and the matching end.

Both foreach and end must appear alone on separate lines. The builtin command continue may be used to continue the loop prematurely and the builtin command break to terminate it prematurely. When this command is read from the terminal, the loop is read once prompting with " foreach? If you make a mistake typing in a loop at the terminal you can rub it out.

Like echo , but the " -n " parameter is not recognized and words are delimited by null characters in the output. Useful for programs which want to use the shell to filename-expand a list of words. The shell rewinds its input as much as possible, searches for a line of the form " label: ", possibly preceded by blanks or tabs, and continues execution after that line.

Prints a statistics line indicating how effective the internal hash table is at locating commands and avoiding exec 's. On machines without vfork , prints only the number and size of hash buckets.

The first form prints the history event list. If n is given only the n most recent events are printed or saved. With -h , the history list is printed without leading numbers.

If -T is specified, timestamps are printed also in comment form. This can produce files suitable for loading with " history -L " or " source -h ". With -r , the order of printing is most recent first rather than oldest first. With -S , the second form saves the history list to filename.

If the first word of the savehist shell variable is set to a number, at most that many lines are saved. If the second word of savehist is set to " merge ", the history list is merged with the existing history file instead of replacing it if there is one and sorted by timestamp. Merging is intended for an environment like the X Window System with several shells in simultaneous use. Currently it succeeds only when the shells quit nicely one after another.

With -L , the shell appends filename , which is presumably a history list saved by the -S option or the savehist mechanism, to the history list. Note that login shells do the equivalent of " history -L " on startup and, if savehist is set, " history -S " before exiting.

If histlit is set, the first and second forms print and save the literal unexpanded form of the history list. The last form clears the history list. With command , runs command such that it will exit on a hangup signal and arranges for the shell to send it a hangup signal when the shell exits. Note that commands may set their response to hangups, overriding hup. Without an argument, causes the non-interactive shell only to exit on a hangup for the remainder of the script. See also Signal Handling and the nohup builtin command.

If expr an expression, as described under Expressions evaluates true, then command is executed. Variable substitution on command happens early, at the same time it does for the rest of the if command. If the specified expr is true then the commands to the first else are executed; otherwise if expr2 is true then the commands to the second else are executed, etc. Any number of else-if pairs are possible; only one endif is needed.

The else part is likewise optional. The words else and endif must appear at the beginning of input lines; the if must appear alone on its input line or after an else.

Adds each shared-library to the current environment. There is no way to remove a shared library. Lists the active jobs. With -l , lists process IDs in addition to the normal information. On TCF systems, prints the site on which each job is executing. The first and second forms sends the specified signal or, if none is given, the TERM terminate signal to the specified jobs or processes.

There is no default job; saying only " kill " does not send a signal to the current job. The third form lists the signal names. Limits the consumption by the current process and each process it creates to not individually exceed maximum-use on the specified resource. If no maximum-use is given, then the current limit is printed; if no resource is given, then all limitations are given.

If the -h flag is given, the hard limits are used instead of the current limits. The hard limits impose a ceiling on the values of the current limits. Only the super-user may raise the hard limits, but a user may lower or raise the current limits in the legal range. Controllable resources currently include if supported by the OS : cputime. Prints the watch shell variable and reports on each user indicated in watch who is logged in, regardless of when they last logged in.

See also watchlog. This is one way to log off, included for compatibility with sh. Lists files like " ls -F ", but much faster. The first form migrates the process or job to the site specified or the default site determined by the system path. Migrating the shell itself can cause unexpected behavior, because the shell does not like to lose its tty. TCF only. Equivalent to " exec newgrp "; see newgrp.

Sets the scheduling priority for the shell to number , or, without number , to 4. With command , runs command at the appropriate priority.

The greater the number, the less cpu the process gets. The superuser may specify negative priority using " nice -number With command , runs command such that it ignores hangup signals. Note that commands may set their response to hangups, overriding nohup. Without an argument, causes the non-interactive shell only to ignore hangups for the remainder of the script. See also Signal Handling and the hup builtin command.

See also the notify shell variable. Controls the action of the shell on interrupts. Without arguments, restores the default action of the shell on interrupts, which is to terminate shell scripts or return to the terminal command input level. With " - ", causes all interrupts to be ignored. With label, causes the shell to execute a " goto label " when an interrupt is received or a child process terminates because it was interrupted.

Without arguments, pops the directory stack and returns to the new top directory. Finally, all forms of popd print the final directory stack, like dirs. The pushdsilent shell variable can be set to prevent this and the -p flag can be given to override pushdsilent. The -l , -n and -v flags have the same effect on popd as on dirs.

Prints the names and values of all environment variables or, with name , the value of the environment variable name.

Without arguments, exchanges the top two elements of the directory stack. With name , pushes the current working directory onto the directory stack and changes to name. If name is " - " it is interpreted as the previous working directory see Filename Substitution. If dunique is set, pushd removes any instances of name from the stack before pushing it onto the stack.

Finally, all forms of pushd print the final directory stack, like dirs. The -l , -n and -v flags have the same effect on pushd as on dirs. Causes the internal hash table of the contents of the directories in the path variable to be recomputed.

This is needed if the autorehash shell variable is not set and new commands are added to directories in path while you are logged in. With autorehash , a new command automatically finds, except in the special case where another command of the same name that is located in a different directory already exists in the hash table. Also flushes the cache of home directories built by tilde expansion. The specified command , which is subject to the same restrictions as the command in the one line if statement above, is executed count times.

The first form prints the scheduled-event list. The sched shell variable may be set to define the format where the scheduled-event list is printed. The second form adds command to the scheduled-event list. It is possible to miss the exact time when the command is to run, but an overdue command will execute at the next prompt.

A command which comes due while the shell is waiting for user input is executed immediately. However, normal operation of an already-running command is not interrupted so that a scheduled-event list element may run. This mechanism is similar to, but not the same as, the at command on some Unix systems. Its major disadvantage is that it may not run a command at exactly the specified time. Its major advantage is that because sched runs directly from the shell, it has access to shell variables and other structures.

This provides a mechanism for changing one's working environment based on the time of day. The first form of the command prints the value of all shell variables. Variables which contain more than a single word print as a parenthesized word list. The second form sets name to the null string.

The third form sets name to the single word. The fourth form sets name to the list of words in wordlist. In all cases the value is command- and filename-expanded. If -r is specified, the value is set read-only. If -f or -l are specified, set only unique words keeping their order.

The fifth form sets the index 'th component of name to word ; this component must already exist. The sixth form lists only the names of all shell variables that are read-only. The seventh form makes name read-only, whether or not it has a value.

The eighth form is the same as the third form, but makes name read-only at the same time. Note, however, that variable expansion happens for all arguments before any setting occurs. See also the unset builtin command. Without arguments, prints the names and values of all environment variables. Given name , sets the environment variable name to value or, without value , to the null string.

Tells the shell to believe that the terminal capability cap as defined in termcap has the value value. No sanity checking is done. Concept terminal users may have to " settc xn no " to get proper wrapping at the rightmost column. Controls which tty modes see Terminal management the shell does not allow to change. The available modes, and thus the display, vary from system to system. With -a , lists all tty modes in the chosen set whether or not they are fixed. Set the experimental version prefix to string , or removes it if string is omitted.

Without arguments, discards argv[1] and shifts the members of argv to the left. It is an error for argv not to be set or have less than one word as value. With variable, performs the same function on variable. The shell reads and executes commands from name. The commands are not placed on the history list. If any args are given, they are placed in argv. An error in a source at any level terminates all nested source commands. With -h , commands are placed on the history list instead of being executed, much like " history -L ".

Stops the specified jobs or processes that are executing in the background. There is no default job; saying only " stop " does not stop the current job.

This is most often used to stop shells started by su. Each case label is successively matched, against the specified string that is first command- and filename-expanded.

If none of the labels match before a "default" label is found, then the execution begins after the default label. Each case label and the default label must appear at the beginning of a line. The command breaksw causes execution to continue after the endsw. Otherwise control may fall through case labels and default labels as in C. If no label matches and there is no default, execution continues after the endsw. Tests if terminal type or the current value of TERM if no terminal type is given has an entry in the hosts termcap or terminfo database.

Prints the terminal type to stdout and returns 0 if an entry is present otherwise returns 1. Executes command which must be a simple command, not an alias, a pipeline, a command list or a parenthesized command list and prints a time summary as described under the time variable. If necessary, an extra shell is created to print the time statistic when the command completes. Without command , prints a time summary for the current shell and its children.

Sets the file creation mask to value , which is given in octal. Common values for the mask are , giving all access to the group and read and execute access to others, and , giving read and execute access to the group and others. Without value, prints the current file creation mask. Removes all aliases whose names match pattern. It is not an error for nothing to be unaliased. Removes all completions whose names match pattern.

It is not an error for nothing to be uncompleted.