I need to read a file line by line but sometimes, depends on condition, jump a number of lines.
How do I do that?
Thank you.
(sorry for my English)
#! /bin/bash
function skip() {
for (( i=0 ; i<$1; ++i )); do
read line
done
}
while read line; do
if [[ "$line" == "#"* ]]; then
skip 2
else
...
fi
done
while read line
do
echo "$line"
if [ "$line" != "As I expect" ]; then
echo "Jumping...";
fi
done
Related
I am working on a project in Bash that takes a live xlsx file, converts it into a csv file, and checks the file to make sure that the data inside it are urls. This is part of a larger progragam that will eventually test each url for domain squatting.
I am having problems with the verification of the string data. I am having to teach myself bash as i go along since this is a self study class. Thanks for the Help!
INPUT=domain3.csv
while IFS= read -r line
do
if [[ "$line" == *".com"*] || [ "$line" == *".net"*] || [ "$line" == *".org"*] || [ "$line" == *".biz"*]];
then echo "$line"
else echo "$line is not an URL"
fi
echo "Finished!"
done
Use the =~ to perform regular expression match:
if [[ $INPUT =~ \.(com|net|org)$ ]]
then
echo $INPUT is a domain
else
echo $INPUT is not a domain
fi
The expression reads that if $INPUT matches a dot (\.), then one of "com", "net", or "org", then end of string ($), then it is a domain.
[[ ... ]] (since bash 4.1) temporarily enables the extglob option, so you can write
if [[ "$line" == *.#(com|net|org|biz)* ]];
You probably don't actually want the trailing *, which would let you match things like foo.comzzz.
A case statement.
#!/bin/sh
while IFS= read -r line; do
case $line in
*.com|*.net|*.org|*.biz)
echo "$line";;
*) printf >&2 '%s is not a url!\n' "$line" ;;
esac
done
Please execute the below code once and then compare it with your's to find out the error.
while IFS= read -r line
do
if [[ "$line" == *".com"* ]] || [[ "$line" == *".net"* ]] || [[ "$line" == *".org"* ]] || [[ "$line" == *".biz"* ]]
then
echo "$line"
else
echo "$line is not an URL"
fi
done < $INPUT
echo "Finished!"
I have two files I am trying to read line by line, but I only want to continue reading from only file or the other on any given iteration of a loop. (I am also unsure how to check for EOF). Here is my pseudocode:
#initialize variables
line1=read <file1.txt
line2=read <file2.txt
#compare lists
while true
do
#check if there is a match
if [[ "$line1" == "$line2" ]]
then
echo match
break
elif [ "$line1" -lt "$line2" ]
then
line1=read <file1.txt # <-SHOULD READ NEXT LINE OF F1
else
line2=read <file2.txt # <-SHOULD READ NEXT LINE OF F2
fi
#Check for EOF
if [[ "$line1" == EOF || "$line2" == EOF ]]
then
break
fi
done
Obviously, as it stands now, this would continue reading just the first line of F1 and F2.
Any help would be greatly appreciated!
You need to open each file once, so that you don't reset the file pointer before each read. read will have a non-zero exit status any time it tries to read past the last line of a file, so you can check for that to terminate the loop.
{
read line1 <&3
read line2 <&4
while true; do
#check if there is a match
if [[ "$line1" == "$line2" ]]; then
echo match
break
elif [ "$line1" -lt "$line2" ]; then
read line1 <&3 || break
else
read line2 <&4 || break
fi
done
} 3< file1.txt 4< file2.txt
A beginner asking for help (:
So, I have a script that checks brackets in a text file and tells whether they are closed correctly. However, I also want to make my script print out the number of the incorrect line (where brackets are closed incorrectly). I have tried counting file lines and then making a nested while loop, however, it doesn't work for me at all ): Are there any simple solutions for this? I would like to leave the LINE counter if that's possible o:
INPUT="$1"
count=0
LINE=0
# Check if file exists
[ ! -f $INPUT ] && { echo "file $INPUT do not exist."; exit ; }
# Count file lines and read every char
while IFS= read -r LINE
do
LINE=$(( LINE + 1 ))
while read -n1 char
do
[ "$char" == "(" ] && (( count++ ))
[ "$char" == ")" ] && (( count-- ))
if [ "$count" -lt 0 ]
then
break
fi
done
done < "$INPUT"
if [ "$count" -lt 0 ]
then
echo "Found a mistake in $LINE line "
else
echo "Everything's correct"
fi
You have a couple of problems:
Your read in the inner loop consumes the input from the file, not from LINE.
The line
LINE=$(( LINE + 1 ))
is really wrong: LINE is the content of the line of your file, and your trying to add 1 to it. Weird.
Your break only breaks the inner loop (it should break two loops). Use break 2 for this.
Here's a working version of your script:
input=$1
count=0
linenb=0
# Check if file exists
[[ -f $input ]] || { echo "Error: file $input do not exist."; exit 1; }
# Count file lines and read every char
while IFS= read -r line; do
((++linenb))
while read -n1 char; do
[[ $char == '(' ]] && ((++count))
[[ $char == ')' ]] && ((--count))
((count>=0)) || break 2
done <<< "$line"
done < "$input"
if ((count<0)); then
echo "Found a mistake in line #$linenb:"
printf '%s\n' "$line"
else
echo "Everything's correct"
fi
Note that I used more ((...)) and [[...]].
I also used lowercase variable names, as your computer isn't deaf: you don't need to shout the name of the variable. (And it's nicer to the eye). And it's good practice to use lowercase variable names, as there's no chance that they clash with Bash's own variables.
I am trying to create an if statement that performs an action when it reads a blank line.
I would assume it would be something like this : if ($line=='\n');then
where line is the line that it is reading from a text file. But this is not working.
while read line; do
if [ "$line" = "" ]; then
echo BLANK
fi
done < filename.txt
or a slight variation:
while read line; do
if [ "$line" ]; then
echo NOT BLANK
else
echo BLANK
fi
done < filename.txt
try this:
if [[ "x$line" == "x" ]]; then...
or
if [[ "$line" =~ "^$" ]]; ...
Or also:
grep -q '.' <<< $line
Returns 1 if line is empty, 0 if non-empty
I have a shell script like this:
cat file | while read line
do
# run some commands using $line
done
Now I need to check if the line contains any non-whitespace character ([\n\t ]), and if not, skip it.
How can I do this?
Since read reads whitespace-delimited fields by default, a line containing only whitespace should result in the empty string being assigned to the variable, so you should be able to skip empty lines with just:
[ -z "$line" ] && continue
try this
while read line;
do
if [ "$line" != "" ]; then
# Do something here
fi
done < $SOURCE_FILE
bash:
if [[ ! $line =~ [^[:space:]] ]] ; then
continue
fi
And use done < file instead of cat file | while, unless you know why you'd use the latter.
cat i useless in this case if you are using while read loop. I am not sure if you meant you want to skip lines that is empty or if you want to skip lines that also contain at least a white space.
i=0
while read -r line
do
((i++)) # or $(echo $i+1|bc) with sh
case "$line" in
"") echo "blank line at line: $i ";;
*" "*) echo "line with blanks at $i";;
*[[:blank:]]*) echo "line with blanks at $i";;
esac
done <"file"
if ! grep -q '[^[:space:]]' ; then
continue
fi
blank=`tail -1 <file-location>`
if [ -z "$blank" ]
then
echo "end of the line is the blank line"
else
echo "their is something in last line"
fi
awk 'NF' file | while read line
do
# run some commands using $line
done
stole this answer to a similar question:
Delete empty lines using sed