pipe then hyphen (stdin) as an alternative to for loop - linux

Question

I wrote a few sed an awk commands to extract a set of IDs that are associated with file names. I would like to run a set of commands using these filenames from id.txt
cat id.txt
14235.gz
41231.gz
41234.gz
I usually write for loops as follows:
for i in $(cat id.txt);
do
command <options> $i
done
I thought I could also do cat id.txt | command <options> -
Is there a way to pipe the output of cat, awk, sed, etc, line by line into a command?

Answer 1

Use a while read loop see Don't read lines wit for
while IFS= read -r line_in_text_file; do
echo "$line_in_text_file"
done < id.txt

Answer 2

Commands don't usually get their filename arguments on standard input. Using - as an argument means to read the file contents from standard input instead of a named file, it doesn't mean to get the filename from stdin.
You can use command substitution to use the contents of the file as all the filename arguments to the command:
command <options> $(cat id.txt)
or you can use xargs
xargs command <options> < id.txt

Answer 3

Is there a way to pipe the output of cat, awk, sed, etc, line by line into a command?
Compound commands can be placed in a pipe, the syntax is not very strict. The usual:
awk 'some awk script' |
while IFS= read -r line; do
echo "$line"
done |
sed 'some sed script'
I avoid reading input line by line using a while read - it's very slow. It's way faster to use awk scripts and other commands.
Command groups can be used to:
awk 'some awk script' |
{ # or '(', but there is no need for a subshell
echo "header1,header2"
# remove first line
IFS= read -r first_line
# ignore last line
sed '$d'
} |
sed 'some sed script'
Remember that pipe command are run in a subshell, so variable changes will not affect parent shell.
Bash has process substitution extension that let's you run a while loop inside parent shell:
var=1
while IFS= read -r line; do
if [[ "$line" == 2 ]]; then
var=2
fi
done <(
seq 10 |
sed '$d'
)
echo "$var" # will output 2

Answer 4

xargs can do this
cat id.txt | xargs command
From xargs help
$ xargs --help
Usage: xargs [OPTION]... COMMAND [INITIAL-ARGS]...
Run COMMAND with arguments INITIAL-ARGS and more arguments read from input.
Mandatory and optional arguments to long options are also
mandatory or optional for the corresponding short option.
-0, --null items are separated by a null, not whitespace;
disables quote and backslash processing and
logical EOF processing
-a, --arg-file=FILE read arguments from FILE, not standard input
-d, --delimiter=CHARACTER items in input stream are separated by CHARACTER,
not by whitespace; disables quote and backslash
...