dodo - scriptable in place file editor

dodo is a work in progress so it is highly recommended you backup any files you are going to modify using dodo.

dodo is a non-interactive scriptable in place file editor.

dodo was born from the need to efficiently edit very large files (16GB plain sql dumps), I was unable to do so using my normal toolset (ed, sed or vim) and I realised that writing a tool specifically for this use case would be very simple.

cd dodo
make
make test

dodo is run and supplied with a single argument representing the filename to work on.

dodo then reads it's commands from stdin, note that dodo is non-interactive so will not start work until it's stdin input is finished (it sees eof).

in dodo all changes are flushed immediately; there are no concepts of 'saving', 'undo' or 'backups'.

dodo is really a very thin wrapper around fread and fwrite.

example dodo usage:

./dodo filename <<EOF
    p          # print 100 bytes
    p5         # print 5 bytes ('hello')
    e/hello/   # expect string 'hello'
    b6         # goto byte 6 in file
    e/world/   # expect string 'world'
    w/marge/   # write string 'marge' (writes over 'world')
    b38        # goto byte 38 in file
    e/sl\/ash/ # expect string 'sl/ash'
    w/slashy/  # write over string 'sl/ash' with 'slashy'
    q          # quit
EOF

each of the commands is explained below in more detail.

dodo currently supports the following commands and syntax:

print

p
pnumber

print specified number of bytes, if number is not specified will default to 100

line:

lnumber

place cursor at the start of 'number'-th line. Warning: this may be expensive in large files

expect:

e/string/

check for 'string' at current cursor position, exit with error if not found.

expect does not move the cursor.

byte:

bnumber

move cursor to absolute byte 'number' within file

write:

w/string/

write 'string' to current cursor position, this will overwrite any characters in the way

write moves the cursor by the number of bytes written

truncate:

truncate the file at the current cursor position. Note that since the cursor can be inside or outside of the file, this can be used to truncate or extend files.

quit:

q

exit dodo, quit is not actually needed as EOF will trigger an implicit quit.

comments: dodo also supports comments

# this is a comment and spans until \n

whitespace:

in dodo whitespace is non-significant except in the case of a newline ('\n') terminating a comment

escape character: a backslash can be used as an escape character, useful mainly when the expected string or replacement string has to include a string delimiter (forward slash)

e/foo\/bar/
w/baz\\qux/

will replace foo/bar with baz\qux

Chris Hall

David Phillips

Tom Ryder