Command Structure¶

med commands attempt to have a syntactically identical form to those of ed(1) or sed(1). Commands consist of an optional address or two optional, comma separated, addresses, followed by a command, which may be abbreviated, possibly followed by a third address or a command specific argument list :

[ address [, address ] ] command [ address | args ]

For example, 1,10p means “print (display) frame 1 through 10” (two addresses), d means “delete the current frame” (no address implies the current frame used as default), and 1,5c5 means “append a copy of frames 1 through 5 at frame 5” (three addresses). The meaning of argument varies for each operation. In med's current state the only valid argument is a filename — for the write, w , command for instance, argument is the name of the file to write to.

Unlike its friends ed(1) and sed(1) med attempts to be fairly user friendly. If an invalid or ambiguous command is given med will tell you so. If med thinks it recognizes a command with invalid arguments a usage statement for the offending command is given. If a particular command fails and med is smart enough to figure out why it will tell you. med will almost ALWAYS immediately terminate when an error occurs while processing commands from a file or the command line. Help is available by using the h command. Usage statements for a particular command may be obtained with: h command name .

Addresses¶

Frames can be addressed in several ways:

nnn

By frame number. Frames in the buffer are numbered relative to the start of the buffer. The first frame is frame 1.

$

The last frame of the buffer.

.

The current frame. med keeps track of the frame on which you last performed an operation. This frame is called the current frame. You can address this frame by typing a “dot” character.

±n

By relative frame number. Address the frame number that is n frames higher, or n frames lower than the current frame.

address±n

An address followed by a plus sign (+) or a minus sign (-), followed by a decimal number, specifies that address plus or minus the indicated number of frames. If the address is omitted, the current frame is used as the base. For example, `31-3' addresses frame 28 in the buffer.

If you do not specify an address for a command to operate on, a command that requires an address supplies one by default, usually the current frame.

A pair of addresses separated by a comma signifies an inclusive range of frames, and the current frame is not changed unless the command changes it.

Commands¶

Only one command may appear per line. Commands may accept zero, one or two addresses, followed by possibly a third address or an argument. Commands that accept up to two addresses regard a third as an error. Likewise, commands that do not accept an argument regard one as an error. Commands may be abbreviated.

In the absence of a second address for a two or three address command the command will regard the second address as the same as the first. For example, 2d is equivalent to 2,2d . The absence of a first address, where required, will result in the current frame being used as the default. The same is true in the absence of a required third address. For example, c is equivalent to .,.c..

The commands q (quit) and e (edit) may be followed by a '!' to override med's user protection.

In the following list of med commands, the default addresses/arguments appear in parentheses; the parenthesized addresses are not part of the command. Unless otherwise noted a command does not change the current frame number.

(1,$)append metafile
Append buffer to a file. Append the addressed frames in the buffer to metafile. If no address is specified the entire buffer is written. If the file does not exist create it.

(.,.) copy (.)

Copy frames. Duplicate the addressed frames in the buffer and append them after the third address. The current frame becomes the destination of the last frame copied.

(.,.)delete

Delete the addressed lines from the buffer. delete accepts one or two addresses; the default is the current frame. The current frame is set to the first frame after the deleted frame(s).

edit metafile

Edit a metafile. The current contents of the buffer, if any, are erased. The named metafile is read in to the buffer. The resulting current frame is the last frame in the buffer. If changes have been made to the buffer since the last write med will refuse the request unless the command is appended with a '!'. edit prints the number of frames in the metafile. If no metafile is given, the current metafile, if any is used. The current frame becomes the last frame in the file.

help command

help. Give a usage message for command . If no command is given, print list of command names with a short description of each.

(.,.)label string
Label the addressed frames with string . The CGM Begin Picture element contained in each metafile frame allows for the encoding of character data. label provides a means for accessing this data.

(.,.)merge

Merge the contents of the second addressed frame on top of the first addressed frame. The first addressed frame is thus changed. The second frame remains the same. The current frame is set to the first addressed frame.

(.,.) move (.)

Move the addressed frames to the first frame following the third address.

(.,.)print

Show the contents of the buffer at the given address. What is actually displayed is information regarding the addressed frames. This information includes: relative frame number within the buffer, the number of records contained in the frame, the starting record for the frame and the contents of the CGM element BEGIN PICTURE . If no address is specified the current frame does not change. Otherwise it becomes the last frame printed.

quit
Quit. Terminate the editing session without saving the buffer contents. In order to save the buffer an explicit write must be performed. If changes to the buffer have been made since the last write med will refuse to terminate unless quit is appended with a '!'.

(.)read metafile
Read in a metafile. Read the contents of metafile into the buffer and append it at the given address. metafile must be a valid NCAR CGM. The resulting current frame is the last frame read in.

(1,$)split<number> outfile
Split the current metafile into number files. The split command attempts to create number metafiles from the addressed frames, each containing approximately n / number frames where 'n' is the total number of addressed frames. The first file is named outfile001.ncgm, the second file is named outfile002.ncgm, and so on lexicographically. If no outfile is given, med is used as the default (output files will be called med001.ncgm, med002.ncgm, etc.).

(1,$)write metafile
Write buffer. Write the addressed frames in the buffer to metafile. If no address is specified the entire buffer is written. If the file does not exist create it. If no file name is specified med uses the last currently remembered file name, if any. The currently remembered file name is the file name from the most recent edit command, or the file name med was invoked with if no edit commands have been issued.

! command

Escape to the shell and execute command. command is a valid UNIX command.