I have a text file with 50 numbers. I want to read 2 lines at at time assign it to variables
input.txt:
129260
129288
129356
129384
read input.txt ( 2 lines at at time)
$VALUE1=129260
$VALUE2=129288
Put a loop to keep on doing it till entire file is read.
This reads in two lines at a time from input.txt, assigns each line to a variable, and displays the values of the variables:
$ while read -r val1 && read -r val2; do echo "val1=$val1 and val2=$val2"; done <input.txt
val1=129260 and val2=129288
val1=129356 and val2=129384
Related
I'm a beginner in bash and here is my problem. I have a file just like this one:
Azzzezzzezzzezzz...
Bzzzezzzezzzezzz...
Czzzezzzezzzezzz...
I try in a script to edit this file.ABC letters are unique in all this file and there is only one per line.
I want to replace the first e of each line by a number who can be :
1 in line beginning with an A,
2 in line beginning with a B,
3 in line beginning with a C,
and I'd like to loop this in order to have this type of result
Azzz1zzz5zzz1zzz...
Bzzz2zzz4zzz5zzz...
Czzz3zzz6zzz3zzz...
All the numbers here are random int variables between 0 and 9. I really need to start by replacing 1,2,3 in first exec of my loop, then 5,4,6 then 1,5,3 and so on.
I tried this
sed "0,/e/s/e/$1/;0,/e/s/e/$2/;0,/e/s/e/$3/" /tmp/myfile
But the result was this (because I didn't specify the line)
Azzz1zzz2zzz3zzz...
Bzzzezzzezzzezzz...
Czzzezzzezzzezzz...
I noticed that doing sed -i "/A/ s/$/ezzz/" /tmp/myfile will add ezzz at the end of A line so I tried this
sed -i "/A/ 0,/e/s/e/$1/;/B/ 0,/e/s/e/$2/;/C/ 0,/e/s/e/$3/" /tmp/myfile
but it failed
sed: -e expression #1, char 5: unknown command: `0'
Here I'm lost.
I have in a variable (let's call it number_of_e_per_line) the number of e in either A, B or C line.
Thank you for the time you take for me.
Just apply s command on the line that matches A.
sed '
/^A/{ s/e/$1/; }
/^B/{ s/e/$2/; }
# or shorter
/^C/s/e/$3/
'
s command by default replaces the first occurrence. You can do for example s/s/$1/2 to replace the second occurrence, s/e/$1/g (like "Global") replaces all occurrences.
0,/e/ specifies a range of lines - it filters lines from the first up until a line that matches /e/.
sed is not part of Bash. It is a separate (crude) programming language and is a very standard command. See https://www.grymoire.com/Unix/Sed.html .
Continuing from the comment. sed is a poor choice here unless all your files can only have 3 lines. The reason is sed processes each line and has no way to keep a separate count for the occurrences of 'e'.
Instead, wrapping sed in a script and keeping track of the replacements allows you to handle any file no matter the number of lines. You just loop and handle the lines one at a time, e.g.
#!/bin/bash
[ -z "$1" ] && { ## valiate one argument for filename provided
printf "error: filename argument required.\nusage: %s filename\n" "./$1" >&2
exit 1
}
[ -s "$1" ] || { ## validate file exists and non-empty
printf "error: file not found or empty '%s'.\n" "$1"
exit 1
}
declare -i n=1 ## occurrence counter initialized 1
## loop reading each line
while read -r line || [ -n "$line" ]; do
[[ $line =~ ^.*e.*$ ]] || continue ## line has 'e' or get next
sed "s/e/1/$n" <<< "$line" ## substitute the 'n' occurence of 'e'
((n++)) ## increment counter
done < "$1"
Your data file having "..." at the end of each line suggests your files is larger than the snippet posted. If you have lines beginning 'A' - 'Z', you don't want to have to write 26 separate /match/s/find/replace/ substitutions. And if you have somewhere between 3 and 26 (or more), you don't want to have to rewrite a different sed expression for every new file you are faced with.
That's why I say sed is a poor choice. You really have no way to make the task a generic task with sed. The downside to using a script is it will become a poor choice as the number of records you need to process increase (over 100000 or so just due to efficiency)
Example Use/Output
With the script in replace-e-incremental.sh and your data in file, you would do:
$ bash replace-e-incremental.sh file
Azzz1zzzezzzezzz...
Bzzzezzz1zzzezzz...
Czzzezzzezzz1zzz...
To Modify file In-Place
Since you make multiple calls to sed here, you need to redirect the output of the file to a temporary file and then replace the original by overwriting it with the temp file, e.g.
$ bash replace-e-incremental.sh file > mytempfile && mv -f mytempfile file
$ cat file
Azzz1zzzezzzezzz...
Bzzzezzz1zzzezzz...
Czzzezzzezzz1zzz...
I had what I thought was a simple concept which I could easily do as I did something similar.
I have an input file input.csv
1a,1b
2a,2b
I would like the following output
Output file 1
This is variable 1 named 1a ok
This is variable 2 named 1b ok
Output file 2
This is variable 1 named 2a ok
This is variable 2 named 2b ok
I thought I could do something similar to below
i=1
while IFS=, read var1 var2; do
echo This is variable 1 named "var1" > filenamei
echo This is variable 2 named "var2" >> filenamei
i=i+1
done </inputfile.csv
I previously wrote code to take a single variable from a long file and write output to a single file and it worked fine. Like below
Input file
a
b
Single output file
This is A
This is B
Script was
while read p;do
echo this is "$p" >>output file
done < input file
Been through lots of different errors but getting nowhere.
It will be easy by configuring double loop: the outer loop to iterate over lines and the inner one for comma-separated fields. Then how about:
#!/bin/bash
i=1
while read -r line; do
ifs_back="$IFS"
IFS=","
set -- $line
for ((j=1; j<=$#; j++)); do
echo This is variable "$j" named "${!j}" >> "filename${i}"
done
IFS="$ifs_back"
i=$((i+1))
done < "inputfile.csv"
Explanations:
In order to split the input line with commas, we temporarily set IFS to "," then assign the fields to positional parameters $1, $2.
The loop counter j for the inner loop starts with 1 and ends with $#1, number of fields.
We can access the value of the positional parameter via ${!j}.
As a clean up of the inner loop, we retrieve IFS and increment i for the next line.
The code above is flexible with #lines and #fields so would work with the input:
1a,1b
2a,2b
3a,3b
as wel as with:
1a,1b,1c
2a,2b,2c
3a,3b,3c
Hope this helps.
I have below output from a text file. This is long file i just copy here some rows only.
HP83904B74E6
13569.06
7705.509999999999
HP4DC2EECAA8
4175.1
2604.13
And i want to print it like below.
HP83904B74E6 13569.06 7705.509999999999
HP4DC2EECAA8 4175.1 2604.13
I have tried by reading the file line by live using while loop and try to store the value of variable e.g. variablename$i so that i can print it like variablename0 and after every 3 line i have used If statement to print the value of variablename0 variablename1 variablename2, but did not work for me.
Use pr:
$ pr -a3t tmp.txt
HP83904B74E6 13569.06 7705.509999999999
HP4DC2EECAA8 4175.1 2604.13
i have tried by reading the file line by live using while loop and try to store the value of variable e.g. variablename$i so that i can print it like variablename0 and after every 3 line i have used If statement to print the value of variablename0 variablename1 variablename2, but did not work for me. I am just learning bash.
while read -r a; do
read -r b;
read -r c;
echo "$a $b $c";
done < file
you get,
HP83904B74E6 13569.06 7705.509999999999
HP4DC2EECAA8 4175.1 2604.13
I'm relatively new to shell scripting and am writing a script to organize my music library. I'm using awk to parse the id3 tag info and am generating a newline separated list like so:
Kanye West
College Dropout
All Falls Down
I want to store each field in a separate variable so I can easily compose some mkdir and mv commands. I've tried piping the output to IFS=$'\n' read artist album title but each variable remains empty. I'm open to producing a different output from awk, but I still want to know how to parse a newline separated list using bash.
Edit:
It turns out that by piping directly to read by doing:
id3info "$filename" | awk "$awkscript" | {read artist; read album; read title;}
WILL NOT WORK. It results in the variables existing in a different scope. I found that using a herestring works best:
{read artist; read album; read title;} <<< "$(id3info "$filename" | awk "$awkscript")"
read normally reads one line at a time. So, if your id3 info is in the file testfile.txt, you can read it in as follows:
{ read artist ; read album ; read song ; } <testfile.txt
echo "artist='$artist' album='$album' song='$song'"
# insert your mkdir and mv commands....
When run on your test file, the above outputs:
artist='Kanye West' album='College Dropout' song='All Falls Down'
You can just read the file into a bash array and loop through the array like so:
IFS=$'\r\n' content=($(cat ${filepath}))
for ((idx = 0; idx < ${#content[#]}; idx+=3)); do
artist=${content[idx]}
album=${content[idx+1]}
title=${content[idx+2]}
done
Or read three lines in a loop.
yourscript |
while read artist; do # read first line of input
read album # read second line of input
read song # read third line of input
: self-destruct if the genre is rap
done
This loop will consume input lines in groups of three. If there is not an even multiple of three lines of input, the reads after that inside the loop will simply fail and the variables will be empty.
You can read the output from awk into an array. E.g.
readarray -t array <<< "$(printf '%s\n' 'Kanye West' 'College Dropout' 'All Falls Down')"
for ((i=0; i<${#array[#]}; i++ )) ; do
echo "array[$i]=${array[$i]}"
done
Produces:
array[0]=Kanye West
array[1]=College Dropout
array[2]=All Falls Down
I've got a text file with an arbitrary number of lines, e.g.:
one line
some other line
an additional line
one more here
I'd like to write a script to reorder those lines based on a given order. e.g.
An input of 2 1 3 4 would swap the first and second lines.
An input of 3 1 2 4 would put the 3rd line first, the 1st line second, the 2nd line third and keep the 4th line fourth.
I could hack something together, but I'm wondering if there's an elegant solution?
I can use either bash or ksh.
You can use sed:
for num in $input ; do
sed $num'!d' file
done
Here's a perl solution:
#!/usr/bin/perl -w
my #lines = <STDIN>; # Read stdin into an array
foreach my $linenum (#ARGV) { # Get the new order from argument list
print $lines[$linenum-1];
}
Run the script as:
./scriptname 2 1 3 4 < inputfile
In awk:
for num in "$#"; do
awk "NF==$num" file
done
Bash-only (don't need to reset IFS if you are putting this in a script):
IFS=$'\n'
lines=( $(<file) )
for num in "$#"; do
echo lines[num-1]
done