Shell Programming and Scripting

I am trying to figure out how to split a file when the data in the new line is different from the current line using a shell script?

For eg..

if my input file contains the following

2341123 ABCAD
2341123 ANCAED
2341123 AVADV
3343434 ASDVAV
3343434 ASDFADF
4231232 ADACVAV
4231232 ADADFADFADFASDF
4343433 ASDGAV
4343433 ADFDFDF

I would like to have 4 files

file 1 should have
2341123 ABCAD
2341123 ANCAED
2341123 AVADV

file 2 should have
3343434 ASDVAV
3343434 ASDFADF

file 3 should have
4231232 ADACVAV
4231232 ADADFADFADFASDF

file 4 should have
4343433 ASDGAV
4343433 ADFDFDF

Is this possible? I am new to the unix world and need help. Any help is much appreciated and thank you in advance.

You can use the awk/nawk command to read the file. Save each different key to test to a compare variable. Then compare $1 to the compare value. If they are different then change your output to point to the next file.

awk -F" " '
BEGIN { KEY=""; NUMBER=0;}
{
if ( $1 == KEY )
{
print $0 >> FILENAME;
}
else
{
NUMBER+=1;
KEY=$1;
FILENAME="file"NUMBER;
print $0 >> FILENAME;
}
NEXT
}' myfile

result is
sh-3.2$ cat file1
2341123 ABCAD
2341123 ANCAED
2341123 AVADV

sh-3.2$ cat file2
3343434 ASDVAV
3343434 ASDFADF

sh-3.2$ cat file3
4231232 ADACVAV
4231232 ADADFADFADFASDF

sh-3.2$ cat file4
4343433 ASDGAV
4343433 ADFDFDF
sh-3.2$

Code:

awk '{f="file_"$1;print > f}' file

Thank you so much.. That worked.