UNIX for Beginners Questions & Answers

 
 paste Allen_Free.txt Allen_Current.txt Allen_Allocated.txt | awk 'function get(field){q=NF/3;for(i=field;i<=NF;i+=q){$field=i>field?$field "/" $i:$field;}} BEGIN{FS=OFS="\t"}  NR>1 {for(j=2;j<=NF/3;j++){get(j)};for(j=NF/3+1;j<=NF;j++){$j=""};sub(/[[:space:]]+$/,X,$0);print

cat script.ksh
COUNT=$(ls *.txt | wc -l)
paste *.txt | awk -vcount="$COUNT" 'function get(field){
							q=NF/count;
							for(i=field;i<=NF;i+=q){
										$field=i>field?$field "/" $i:$field;
							       		       }
                                                       } 
                   NR>1               {
					for(j=2;j<=NF/count;j++)   {
								get(j)
                                                               };
					for(j=NF/count+1;j<=NF;j++){
								$j=""
							       };
                                        sub(/[[:space:]]+$/,X,$0);
					print
 				      }
                   NR==1              {
					for(j=1;j<=NF/count;j++)   {
								printf("%s\t",$j);
                                                                   }
					print X;
				      }
		                   '  FS=OFS="\t"

cat script.ksh
COUNT=$(ls *.txt | wc -l)
paste *.txt | awk -vcount=$COUNT 'function get(field){q=NF/count;for(i=field;i<=NF;i+=q){$field=i>field?$field "/" $i:$field;}} NR>1{for(j=2;j<=NF/count;j++){get(j)};for(j=NF/count+1;j<=NF;j++){$j=""};sub(/[[:space:]]+$/,X,$0);print} NR==1{for(j=1;j<=NF/count;j++){printf("%s\t",$j)}print X;}'

COUNT=$(ls *.txt | wc -l) #### Creating a variable named COUNT(in shell) and it's value will be number of .txt files. If you want to hardcode files which you showed in my code previously then you could ignore this variable and could hardcode file names with paste command along with subsituting the count variable with number of files in awk code too.
paste *.txt               #### Using paste command with all files whose extension is .txt so that it will concatenate their contents as per line numbers.
|                         #### Using pipe here to send the standard output of paste command to awk command as standard input.
awk                       #### Starting awk 
-vcount=$COUNT            #### -v option is used to define ann awk's variable. So here I am making count variable which will have values of SHELL variable named COUNT's value init. This is the way where we could set a shell's variable's value to an awk's variable too.
'function get(field)      #### starting a function here, as we all know in function we could write a logic which we need to perform several times and could save our time and could make code neat and clear, so creating a function for same. Function name is get. passing a value to it called field as by name itself it is clear we are going to pass field into it.
{q=NF/count;              #### creating a variable named q whose value is NF/count where NF is number of fields and it is an awk's in-built variable which gives number of fields into any line/record. so q will have actually number of fields for a single file. Here you have a;ready mentioned that number of fields will be equal in each Input_file so I am dividing TOTAL number of fields with TOTAL number of Input_files so that could get 1 Input_file's number of fields.
for(i=field;i<=NF;i+=q)   #### starting a for loop here whose syntax will be always the usual one for(variable initilization,condition,variable decrement/increment). Similarly we are starting a variabled named i whose value will be equal to variable field(which we are passing to function) and till the value of NF(number of fields in current line/record) it will execute this for loop.
{$field=                  #### Making values of $field where $field defines, let's say we have field variable's value as 2 then $2 defines 2nd field of current line etc.
i>field                   #### checking here condition if i's value is greater than variable field.
?                         #### ? is a well known ternary operator which defines the next statements will be executing if above condition is TRUE.
$field "/" $i             #### setting value of $field into $field "/" $i now.
:                         #### : is a well known ternary operator which defines that statements which are coming next will be executed because condition showed 2 steps above is NOT TRUE.
$field;}}                 #### keeping the value of $field as same $field.
NR>1                      #### Now coming into main section where we are checking if value of NR>1 where NR is awk's built in variable which defines the number of records in a line/record, so I am making sure we are not executing further statements while line number is one which is your header line.
{for(j=2;j<=NF/count;j++) #### starting a for loop here which wil run till variable j's value if less than and equal to value of NF/count.
{get(j)};                 #### Calling function get which we created and explained above for each field of each record/line.
for(j=NF/count+1;j<=NF;j++) #### Starig a for loop whic will run till the value of variable j is less than and equal to value of NF/count+1.
{$j=""};                  #### So I am nullifying the fields, so basically what I am doing is since we need to only fields depending on 1 Input_file so I am Nullifying extra fields now, whose value already been concatinated to needed fields already above.
sub(/[[:space:]]+$/,X,$0);#### substituting the space at last to NULL, when we wil Nullify the fields then at last space will be there so removing it completly with sub which is awk's in-built functionality whose syntax is sub(/pattern/variable/,"new value",line/record/variable).
print}                    #### Finally printing the value of newly modified fields which is requirement.
NR==1{                    #### checking here condition when NR==1 means when 1st line is there then only execute further statements.
for(j=1;j<=NF/count;j++){ #### starting a for loop till variable j's value is less than or equal to value of NF/count+1.
printf("%s\t",$j)}        #### printing the value of fields here.
print X;}'                #### printing value of a NULL value variable, basically to get a new line after headers are printed by above for loop.