Bash - Multiple conditions in a for loop - linux

Question

I'm trying to do a for loop with multiple conditions and I didn't find any information about how to do it on the web
I'm sorry for the stupid questions, but I just started programming in linux
what am I doing wrong here?
#!/bin/bash
j=0
for line in `cat .temp_` || j in `seq 0 19`
do
...
done
the error says wrong syntax and that I can't use ||
Thanks a lot

Answer 1

for line in `cat .temp_`
do
if ! grep -Fxq $line $dictionary && [ $j -lt 20 ]
then
echo $line >> $dictionary
j=$((j+1))
fi
[ $j -gt 20 ] && break
done
You can't check a condition in a for loop in shell. You must do it in a extra statement.
In this case so:
[ $j -gt 20 ] && break
Another solution, without break:
while read line && [ $j -lt 20 ]
do
if ! grep -Fxq $line $dictionary && [ $j -lt 20 ]
then
echo $line >> $dictionary
j=$((j+1))
fi
done < .temp_

Answer 2

You are trying to combine two different styles of for-loops into one. Instead, just break if the value of j becomes too large:
j=0
while read -r line; do
[[ j >= 20 ]] && break
...
done < ._temp
(This, by the way, is the preferred way to iterate over a file in bash. Using a for-loop runs into problems if the file is too large, as you essentially building a command line using the entire contents of the file.)
[UPDATE: the following is based on my conjecture as to the purpose of the loop. See Calculate Word occurrences from file in bash for the real context.]
Actually, you can dispense with the loop. You are looking for at most 20 lines from .temp_ that do not already appear in the file whose name is in dictionary, right?
sort -u .temp_ | grep -f $dictionary -Fx -v -m 20 >> $dictionary
This will call grep just once, instead of once per line in .temp_.

Answer 3

A simple nested for-loop?
for line in `cat file`; do for j in {0..19}; do
your_commands
done; done
If I understand you correctly (you want to run a command on every line 20 times).

Answer 4

Once I need to process all files inside a directory, but only until nth file or until all is processed:
count=1
nth=10
for f in folder/*; do
((count++))
# process $f
if [[ $count -gt $nth ]]
then
break
fi
done