NAME

edinplace - edit a file in place

SYNOPSIS

edinplace [--error=code] [[--file=file] command [arg ...]]

DESCRIPTION

edinplace runs command with its input from file (or standard input by default), and then replaces the contents of file with the output of command. To the extent possible, edinplace attempts to exit with the same status as command.

If edinplace is run on standard input (no --file option), it must inherit a file descriptor 0 that is open for both reading and writing. When processing standard input, if edinplace does not encounter a fatal error, it rewinds its standard input to offset 0 before exiting. Thus, a script can first run edinplace command, then run another filter command such as grep, and the resulting output will be the output of grep on command's output.

If no command is specified, edinplace just rewinds its standard input to file offset 0. In this case, it is an error to supply the --file option. Of course, rewinding only works when standard input is a real file (as opposed to a pipe or device).

There are two options:

--error=code (-x code): Ordinarily, edinplace attempts to exit with the same status as command. However, if edinplace encounters some fatal error (such as being unable to execute command), it will exit with status code. The default value is 1. The range of valid exit codes is 1-255, inclusive.
--file=file (-f file): Specifies that file should be edited. Otherwise, edinplace will edit its standard input (which must be opened for both reading and writing).
--skipfrom: Skip the first line of the file if it starts "From ". If edinplace is run without a command, positions the file offset at the start of the second line of the file. If edinplace is run with a command, then the first line of the file is neither fed to the command, nor overwritten. This option is useful for running edinplace over mail files, which sometimes start with a "From " line specifying the envelope sender of the message. Since "From " is not part of the message header, just a Unix convention, some programs are confused by the presence of that line. Note that if you specify a command, then edinplace resets the file offset to 0 upon exiting, even if the --skipfrom option was present.

EXAMPLES

The following command prepends the string "ORIGINAL: " to the beginning of each line in text file message:

edinplace -f message sed -e 's/^/ORIGINAL: /'

The following command runs the spamassassin mail filter program on a mail message stored in file message, replacing the contents of message with spamassassin's annotated output, and exiting with code 100 if spamassassin thinks the message is spam. If edinplace encounters any fatal errors, it will exit with code 111.

edinplace -x 111 -f message spamassassin -e 100

(spamassassin reads a mail message on standard input and outputs an annotated copy of the message including information about whether or not the message is likely to be spam and why. The -e option to spamassassin specifies what exit status spamassassin should use if the message appears to be spam; edinplace will use the same exit code as the program it has run.)

To run spamassassin on incoming mail before accepting the mail from the remote client, place the following line in an appropriate Mail Avenger rcpt file as the last command executed:

    bodytest edinplace -x 111 spamassassin -e 100

BUGS

edinplace does not make a copy of the file being edited, but rather overwrites the file as it is being processed. At any point where command has produced more output than it has consumed input from the file, edinplace buffers the difference in memory. Thus, a command that outputs large amounts of data before reading the input file can run edinplace out of memory. (A program that outputs data as it reads even a very large file should be fine, however.)

If command crashes or malfunctions for any reason, you will likely lose the input file, since edinplace will view this as a program that simply outputs the empty file.

AUTHOR