Looping through the content of a file in Bash

Question

How do I iterate through each line of a text file with Bash?

With this script:

echo \"Start!\"
for p in (peptides.txt)
do
    echo \"${p}\"
done
         


        

Answer 1

One way to do it is:

while read p; do
  echo "$p"
done 

As pointed out in the comments, this has the side effects of trimming leading whitespace, interpreting backslash sequences, and skipping the last line if it's missing a terminating linefeed. If these are concerns, you can do:

while IFS="" read -r p || [ -n "$p" ]
do
  printf '%s\n' "$p"
done < peptides.txt

---

Exceptionally, if the loop body may read from standard input, you can open the file using a different file descriptor:

while read -u 10 p; do
  ...
done 10

Here, 10 is just an arbitrary number (different from 0, 1, 2).