I am trying to read a text file-"info.txt" which contains the following information
info.txt
1,john,23
2,mary,21
what I want to do is to store each columns into a variable and print any one of the columns out.
I know this may seems simple to you guys but I am new to writing bash script, I only know how to read the file but I don't know how to delimit the , away and need help. Thanks.
while read -r columnOne columnTwo columnThree
do
echo $columnOne
done < "info.txt"
output
1,
2,
expected output
1
2
You need to set the record separator:
while IFS=, read -r columnOne columnTwo columnThree
do
echo "$columnOne"
done < info.txt
Is good to check if the file exists too.
#!/bin/bash
INPUT=./info.txt
OLDIFS=$IFS
IFS=,
[ ! -f $INPUT ] && { echo "$INPUT file not found"; exit 99; }
while read -r columnOne columnTwo columnThree
do
echo "columnOne : $columnOne"
echo "columnTwo : $columnTwo"
echo "columnThree : $columnThree"
done < $INPUT
IFS=$OLDIFS
Related
I am looking for a bash script which reads the file content and it should echo the output as mentioned below:
Input File: file.txt
host1a
host2b
host3c
host4e
I want my output like:
--START--
opt1:host1a
opt2:host2b
opt3:host3c
opt4:host4e
--END--
there is a many possibilities, try this way for example.
#!/bin/bash
opt="1";
while read line;
do
if [ ! -z "$line" ]
then
echo "opt$opt:$line"
opt=$(($opt+1))
fi
done <your_input_file.txt
This seems simple, list the directory from the first field then list the directory from the second field. The fields from the input file are comma separated, e.g.: XXXX1111111111112222,cool.com.
I run the command:
./list_directories some_file.csv
The list_directories script is this:
#!/bin/bash
INPUT=$1
OLDIFS=$IFS
IFS=,
[ ! -f $INPUT ] && { echo "$INPUT file not found"; exit 99; }
while read WORKING STORE
do
echo $STORE
ls $STORE
echo $WORKING
ls $WORKING
done < $INPUT
IFS=$OLDIFS
Here's the output:
/pathtothe/som/coolplace/Imlookingfor/cool.com/place/123/XXXX1111111111112222 : No such file or directorye/Imlookingfor/cool.com/place/123/XXXX1111111111112222 /pathtothe/som/coolplace/Imlookingfor/cool.com/placing/123/XXXX1111111111112222 fileindir.txt otherfileindir.txt lastofthefilesindir.txt
I know that both directories exist. Not sure if I'm getting caught up on the loop or on the IFS.
I'm new to bash scripting and I'm asking for a little help !
I've got a little scipt in bash that is not making what I want (but almost) and the behavior of my echo command seems strange to me, look at it :
TST='test'
TEST="${ADDR[3]}"_"$TST"
echo $TEST
#result : _test
echo ${ADDR[3]}
#result : 5
How can you explain these results ? Thanks in advance :)
My ADDR var is defined like this :
#parsing the read line, split on whitespace
IFS=' ' read -ra ADDR <<< "$line"
Here is my complete script :
#!/bin/bash
NUMBER=2
{ read ;
while IFS= read -r line; do
echo "$NUMBER : $line"
IFS=' ' read -ra ADDR <<< "$line"
#If the countdown is set to 0, launch the task ans set it to init value
if [ ${ADDR[0]} == '0' ]; then
#task launching
echo `./${ADDR[1]}.sh ${ADDR[2]} &`
TST='test'
TEST=${ADDR[3]}_$TST
echo $TEST
VAR=$(echo -E "${ADDR[3]}" | tr -d '\n')
#countdown set to init value
sed -i "$NUMBER c $VAR ${ADDR[1]} ${ADDR[2]} ${ADDR[3]}" listing.txt
else
sed -i "$NUMBER c $((ADDR-1)) ${ADDR[1]} ${ADDR[2]} ${ADDR[3]}" listing.txt
fi
((NUMBER++))
done } < listing.txt
Answer: the following is fine,
TEST="${ADDR[3]}"_"$TST"
Although I would recommend.
TEST="${ADDR[3]}_${TST}"
What you need to do is dump ${ADDR[3]} before this statement and confirm that ADDR holds the expected values. You may as well dump the entire array with indexes and confirm all entries
for ((i=0; i<${#ADDR[#]}; i++)); do
printf "ADDR[%3d] %s\n" "$i" "${ADDR[$i]}"
done
This will help isolate the issue. Sorry for the earlier answer. Lesson [sleep 1st: answer 2nd]
I'm trying to write a small script that will count entries in a log file, and I'm incrementing a variable (USCOUNTER) which I'm trying to use after the loop is done.
But at that moment USCOUNTER looks to be 0 instead of the actual value. Any idea what I'm doing wrong? Thanks!
FILE=$1
tail -n10 mylog > $FILE
USCOUNTER=0
cat $FILE | while read line; do
country=$(echo "$line" | cut -d' ' -f1)
if [ "US" = "$country" ]; then
USCOUNTER=`expr $USCOUNTER + 1`
echo "US counter $USCOUNTER"
fi
done
echo "final $USCOUNTER"
It outputs:
US counter 1
US counter 2
US counter 3
..
final 0
You are using USCOUNTER in a subshell, that's why the variable is not showing in the main shell.
Instead of cat FILE | while ..., do just a while ... done < $FILE. This way, you avoid the common problem of I set variables in a loop that's in a pipeline. Why do they disappear after the loop terminates? Or, why can't I pipe data to read?:
while read country _; do
if [ "US" = "$country" ]; then
USCOUNTER=$(expr $USCOUNTER + 1)
echo "US counter $USCOUNTER"
fi
done < "$FILE"
Note I also replaced the `` expression with a $().
I also replaced while read line; do country=$(echo "$line" | cut -d' ' -f1) with while read country _. This allows you to say while read var1 var2 ... varN where var1 contains the first word in the line, $var2 and so on, until $varN containing the remaining content.
Always use -r with read.
There is no need to use cut, you can stick with pure bash solutions.
In this case passing read a 2nd var (_) to catch the additional "fields"
Prefer [[ ]] over [ ].
Use arithmetic expressions.
Do not forget to quote variables! Link includes other pitfalls as well
while read -r country _; do
if [[ $country = 'US' ]]; then
((USCOUNTER++))
echo "US counter $USCOUNTER"
fi
done < "$FILE"
minimalist
counter=0
((counter++))
echo $counter
You're getting final 0 because your while loop is being executed in a sub (shell) process and any changes made there are not reflected in the current (parent) shell.
Correct script:
while read -r country _; do
if [ "US" = "$country" ]; then
((USCOUNTER++))
echo "US counter $USCOUNTER"
fi
done < "$FILE"
I had the same $count variable in a while loop getting lost issue.
#fedorqui's answer (and a few others) are accurate answers to the actual question: the sub-shell is indeed the problem.
But it lead me to another issue: I wasn't piping a file content... but the output of a series of pipes & greps...
my erroring sample code:
count=0
cat /etc/hosts | head | while read line; do
((count++))
echo $count $line
done
echo $count
and my fix thanks to the help of this thread and the process substitution:
count=0
while IFS= read -r line; do
((count++))
echo "$count $line"
done < <(cat /etc/hosts | head)
echo "$count"
USCOUNTER=$(grep -c "^US " "$FILE")
Incrementing a variable can be done like that:
_my_counter=$[$_my_counter + 1]
Counting the number of occurrence of a pattern in a column can be done with grep
grep -cE "^([^ ]* ){2}US"
-c count
([^ ]* ) To detect a colonne
{2} the colonne number
US your pattern
Using the following 1 line command for changing many files name in linux using phrase specificity:
find -type f -name '*.jpg' | rename 's/holiday/honeymoon/'
For all files with the extension ".jpg", if they contain the string "holiday", replace it with "honeymoon". For instance, this command would rename the file "ourholiday001.jpg" to "ourhoneymoon001.jpg".
This example also illustrates how to use the find command to send a list of files (-type f) with the extension .jpg (-name '*.jpg') to rename via a pipe (|). rename then reads its file list from standard input.
I am having a bash script which is something like following,
cat filename | while read line
do
read input;
echo $input;
done
but this is clearly not giving me the right output as when I do read in the while loop it tries to read from the file filename because of the possible I/O redirection.
Any other way of doing the same?
Read from the controlling terminal device:
read input </dev/tty
more info: http://compgroups.net/comp.unix.shell/Fixing-stdin-inside-a-redirected-loop
You can redirect the regular stdin through unit 3 to keep the get it inside the pipeline:
{ cat notify-finished | while read line; do
read -u 3 input
echo "$input"
done; } 3<&0
BTW, if you really are using cat this way, replace it with a redirect and things become even easier:
while read line; do
read -u 3 input
echo "$input"
done 3<&0 <notify-finished
Or, you can swap stdin and unit 3 in that version -- read the file with unit 3, and just leave stdin alone:
while read line <&3; do
# read & use stdin normally inside the loop
read input
echo "$input"
done 3<notify-finished
Try to change the loop like this:
for line in $(cat filename); do
read input
echo $input;
done
Unit test:
for line in $(cat /etc/passwd); do
read input
echo $input;
echo "[$line]"
done
I have found this parameter -u with read.
"-u 1" means "read from stdout"
while read -r newline; do
((i++))
read -u 1 -p "Doing $i""th file, called $newline. Write your answer and press Enter!"
echo "Processing $newline with $REPLY" # united input from two different read commands.
done <<< $(ls)
It looks like you read twice, the read inside the while loop is not needed. Also, you don't need to invoke the cat command:
while read input
do
echo $input
done < filename
echo "Enter the Programs you want to run:"
> ${PROGRAM_LIST}
while read PROGRAM_ENTRY
do
if [ ! -s ${PROGRAM_ENTRY} ]
then
echo ${PROGRAM_ENTRY} >> ${PROGRAM_LIST}
else
break
fi
done