Shell Programming and Scripting

.I 1
.T
Preliminary Report-International Algebraic Language
.B
CACM December, 1958
.A
Perlis, A. J.
Samelson,K.
.N
CA581203 JB March 22, 1978  8:28 PM
.I 2
.T
Extraction of Roots by Repeated Subtractions for Digital Computers
.B
CACM December, 1958
.A
Sugai, I.
.N
CA581202 JB March 22, 1978  8:29 PM

.T
Preliminary Report-International Algebraic Language
.N
CA581203 JB March 22, 1978  8:28 PM

.T
Extraction of Roots by Repeated Subtractions for Digital Computers
.N
CA581202 JB March 22, 1978  8:29 PM

awk '/^\.I/ {_2="file"$2".txt"} /^\.T|^\.N/{_1=$0;getline;print "echo -e \""_1"\\n"$0"\">>"_2 }' inputfile | bash

bash: line 4321: syntax error near unexpected token `('
bash: line 4321: `echo -e ".T\nAn Algorithm for the Blocks and Cutnodes of a Graph (Corrigendum)">>file2161.txt'

awk '
  /^\.I/ {
    _2="file"$2".txt"
  }
  /^\.T|^\.N/ {
   _1=$0;
   getline;
   print _1  "\n" $0 >> _2
  }
' inputfile

awk '/^\.I/ {_2="file"$2".txt"} /^\.T|^\.N/{_1=$0;getline;print _1"\n"$0 >> _2  }' infile