how to replace multiple text line with new text - bash

Question

I have:
SIESTA_ARCH = unknown
CC = gcc
FPP = $(FC) -E -P -x c
FC = gfortran
and I want to replace this by
SIESTA_ARCH = amd64 (x86_64)
CC = mpicc
FPP = $(FC) -E -P -x c
FC = mpif90

Answer 1

I guess next solution is working for you (edited solution according to answers of the PO):
script.sed
#!/bin/sed -f
/^SIESTA_ARCH = unknown/,/^FC =/{
s/^SIESTA_ARCH =.*/SIESTA_ARCH = amd64 (x86_64)/
s/^CC =.*/CC = mpicc/
s/^FC =.*/FC = mpif90/
}
Invoke as ./script.sed Makefile to see the results on the standard output or as ./script.sed -i Makefile to update the file Makefile.
This solution will change all the occurences of SIESTA_ARCH = unknown and the next line block until a line beginning with FC = into the new values.

Answer 2

In bash you can define a function like this (just execute this one-liner in a terminal or script):
function repl() { FIND="$2" REPLACE="$3" ruby -p -i -e "gsub(ENV['FIND'], ENV['REPLACE'])" "$1"; }
Then you can replace whatever literal strings you want in whatever file, e.g.:
repl ~/Code/Makefile 'SIESTA_ARCH = unknown' 'SIESTA_ARCH = amd64 (x86_64)'
repl ~/Code/Makefile 'CC = gcc' 'CC = mpicc'
repl ~/Code/Makefile 'FC = gfortran' 'FC = mpif90'
Note that this will replace all occurrences of such strings in the specified file.

Answer 3

If you have ed
cat script.ed
H
g/^\(SIESTA_ARCH =\)\(.\+\)$/s//\1 amd64 (x86_64)/
g/^\(CC =\)\(.\+\)$/s//\1 mpicc/
,p
Q
Using the script against your file.
ed -s Makefile < script.ed
Output
SIESTA_ARCH = amd64 (x86_64)
CC = mpicc
FPP = $(FC) -E -P -x c
FC = gfortran
Now change ,p Q to w and q To edit the file in-place.
H
g/^\(SIESTA_ARCH =\)\(.\+\)$/s//\1 amd64 (x86_64)/
g/^\(CC =\)\(.\+\)$/s//\1 mpicc/
w
q
ed -s Makefile < script.ed