shell scripting do loop

Question

Sorry Im new to unix, but just wondering is there anyway I can make the following code into a loop. For example the file name would change every time from 1 to 50

My script is

cut -d ' ' -f5- cd1_abcd_w.txt > cd1_rightformat.txt ;
sed 's! \([^ ]\+\)\( \|$\)!\1 !g' cd1_rightformat.txt ;
sed -i 's/ //g' cd1_rightformat.txt; 
cut -d ' ' -f1-4 cd1_abcd_w.txt > cd1_extrainfo.txt ;

I would like to make this into a loop where cd1_abcd_w.txt would then become cd2_abcd_w.txt and output would be cd2_rightformat.txt etc...all the way to 50. So essentially cd$i.

Many thanks

Answer 1

In bash , you can use brace expansion:

for num in {1..10}; do
    echo ${num}
done

Similar to a BASIC for i = 1 to 10 loop, it's inclusive at both ends, that loop will output the numbers 1 through 10.

You then just replace the echo command with whatever you need to do, such as:

cut -d ' ' -f5- cd${num}_abcd_w.txt >cd${num}_rightformat.txt
# and so on

---

If you need the numbers less than ten to have a leading zero, change the expression in the for loop to be {01..50} instead. That doesn't appear to be the case here but it's very handy to know.

---

Also in the not-needed-but-handy-to-know category, you can also specify an increment if you don't want to use the default of one:

pax> for num in {1..50..9}; do echo ${num}; done
1
10
19
28
37
46

(equivalent to the BASIC for i = 1 to 50 step 9 ).

Answer 2

This should work:

for((i=1;i<=50;i++));do
cut -d ' ' -f5- cd${i}_abcd_w.txt > cd${i}_rightformat.txt ;
sed 's! \([^ ]\+\)\( \|$\)!\1 !g' cd${i}_rightformat.txt ;
sed -i 's/ //g' cd${i}_rightformat.txt; 
cut -d ' ' -f1-4 cd${i}_abcd_w.txt > cd${i}_extrainfo.txt ;
done

Answer 3

This would work in bash:

for in in $(seq 50)
do
cut -d ' ' -f5- cd$i_abcd_w.txt > cd$1_rightformat.txt;
sed 's! \([^ ]\+\)\( \|$\)!\1 !g' cd$i_rightformat.txt;
sed -i 's/ //g' cd$i_rightformat.txt; 
cut -d ' ' -f1-4 cd$i_abcd_w.txt > cd$i_extrainfo.txt;
done