med
Description
med is a frame-level, metafile editor designed to
resemble syntactically UNIX's sed and ed. med
operates on a copy of filename, called a buffer, and
overwrites a file only when you issue the w (write)
command. med provides line oriented editing
commands to display or delete frames from the buffer, to move, copy or
merge frames within the buffer, or to write frames from and read
frames into the buffer. By default med reads in
commands from standard input.
Synopsis
med
[ -e command ]*
[ -f sfilename ]
[ -l local_dir ]
[ -V ]
filename
Options
- -e command
- command is a single med
command. The valid med commands are discussed in the
Commands section below. Multiple -e
options may appear on a single command line. Be careful to use quotes
if your command contains spaces or metacharacters that might be
interpreted by the shell. When this option is used
med does not enter interactive mode. It simply
performs the given commands and then exits.
- -f sfilename
- Execute the med line-separated list of commands in the file
sfilename. After the commands are exhausted
med will exit.
- -l local_dir
- Use
local_dir as the tmp directory for scratch disk space. If
this option is not specified med will use the value
of the $NCARG_TMP or the $TMPDIR environment
variable. See ncargintro for a
discussion on NCAR Graphics environment variables.
- -V
- Print the version number and then exit.
Usage
Command structure
med commands attempt to have a syntactically
identical form to those of ed (1) 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 addres or a
comman specific argument list:
[ address [, address ] ] command
[ address | args ]
If only one address is specified, operations are performed on
that frame. If two address es are specified,
med performs the operation on the inclusive range of
frames. If no address is specified then the current frame is
used as a default. The exception to this are the w
(write) and the a (append) commands. The default
address for w is the entire buffer.
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.
Environment
- NCARG_TMP
- If set, this environment variable contains a directory path to be used for
temporary files. On most systems the default is
/tmp.
Files
- /tmp/cgm_tools.#*
- temporary; # is the process id.
Examples
To concatenate the files ncgm1, ncgm2, and
ncgm3 into a single file ncgm123 one might
use the following:
% med -e 'r ncgm1' -e 'r ncgm2' -e 'r ncgm3' -e 'w ncgm123'
Or one could pass the following script to med as a
-f scriptfile option or enter the commands
interactively.
r ncgm1
r ncgm2
r ncgm3
w ncgm123
To Overlay the contents of frame 5 on top of frame
4 from a file ncgm1 one could
execute:
% med -e '4,5 me' -e 'w!' ncgm1
See also
cgm, ed, sed
Bugs
med
does not understand filenames that begin with a digit or a period.
Caveats
The append, read and merge
commands may produce surprising results. A CGM may contain a set of
global graphical primitive attributes that are applied to every frame
in a file. Thus reading frames in from a file with different global
attributes than the current working file may not produce the desired
effect. The same is true when appending frames to a previously
existing file. Similarly, the CGM standard specifies that graphical
attributes specified within a metafile frame affect all succeeding
primitives. Thus a frame which is the product of the
merge command may appear differently than expected.
Copyright
Copyright © 1987-1999
University Corporation for Atmospheric Research
The use of this
software and documentation is governed by a License Agreement.