This question already has answers here:
Shell script read missing last line
(7 answers)
Closed 6 years ago.
I am having some difficulty understand why i'm not able to enter my while read j loop. The goal of my program is to enter files 1-5 and calculate the sum of the numbers in each file. The output i'm getting is showing me that the read j line is executed, however the while loop isn't entered. This doesn't make intuitive sense to me, since the while condition would be true if the line is read. Heres the output, and the snippet of program below:
in for loop
file1
in for loop
1 9 6 3 3 6
file2
in for loop
1 3 7 6 4 4
file3
in for loop
1 4 8 8 2 4
file4
in for loop
1 5 9 9 1 7
file5
Code:
for (( n=0;n<$columns;n++ ))
do
echo "in for loop"
echo $j
filename="file$counter"
echo "$filename"
#while reading line from current file, take the numbers and find the sum
while read j
do
echo "in while loop"
for number in $j
do
sum=$(($sum + $number))
done
echo "Sum: $sum"
done < $filename
counter=$(($counter + 1))
done
Solution: Add a newline character to the end of the line in each file, read looks for the newline character to recognize a line.
Related
This question already has an answer here:
Command Line Arguments vs Input - What's the Difference?
(1 answer)
Closed 12 months ago.
I have for example a user with a set of numbers. How can I make bash add them together?
Example in one go the user enters
(The amount of numbers they enter is up to them and it is unknown)
bash file 3 1 5 2 2 4
How can I make bash return 17 directly from that example?
I tried
#!/usr/bin/env sh
sum=0
while read number && [ -n "$number" ]; do
sum=$((sum + ${number/#-}))
echo "$sum"
done
But this is not clean and it is returning
$ bash file
3
3
1
4
5
9
2
11
2
13
4
17
I instead want the user to only place their numbers in 1 go and not be there to put more and more numbers
Instead of having them excute the command like I have it like
bash file
1
3
4
etc
instead I want to do it in 1 go
bash file 1 3 5 6
How?
You can loop through all script arguments and calculate sum:
#!/usr/bin/env sh
sum=0
for i in "$#"; do
sum=$(( $sum + $i ))
done
echo $sum
Running with your example:
$ bash sum 3 1 5 2 2 4
17
I wrote a simple code via bash script,
Code 1
for((i=1;i<=10;i++))
do
echo $i
i=$((i+1))
echo $i
i=$((i+2))
done
output of Code 1
1
2
5
6
9
10
Code 2
for i in {1..10}
do
echo $i
i=$((i+1))
echo $i
i=$((i+2))
done
output of Code 2
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
10
11
I'm just wondering, why outputs are not same ?
Thnx in advance
With in, the variable iterates over the list. You can change its value in the loop, but when the next iteration starts, the next value will be assigned to it, regardless of what value you assigned to it. (And I can't imagine any other behaviour: should the shell try to guess how far in the list you want to jump? What if the value is repeated, or not present in the list at all?)
With the C-style for, the variable is initialized, and at each iteration, its value is changed and the condition checked. There's no list of values, only the condition to end the loop.
These are not shorthand for each other: They're completely different code, and expected to behave in different ways.
{1..10} is just shorthand for 1 2 3 4 5 6 7 8 9 10; when you run for i in 1 2 3 4 5 6 7 8 9 10, you're explicitly assigning those exact values to i in turn, overwriting whatever else was previously there.
By contrast, for ((i=1; i<=10; i++)) is providing three separate statements: An initializer (i=1), telling it what to do to start the loop; a check (i<=10) to tell it how to determine whether the loop is finished; and an update (i++), telling it what to do between loop iterations. These are completely arbitrary commands, and you can put any arithmetic expression you want in these positions.
The for((i=1;i<=10;i++)) loop could be rewritten as such:
i=1 # for loop's 'i=1'
while [[ "${i}" -le 10 ]] # for loop's 'i<=10'
do
echo $i
i=$((i+1))
echo $i
i=$((i+2))
((i++)) # for loop's 'i++'
done
This generates ... you guessed it ...
1
2
5
6
9
10
Charles Duffy has already expanded the for i in {1..10} loop to show how that behaves.
This question already has answers here:
How to merge two files consistently line by line
(6 answers)
How can I extract a predetermined range of lines from a text file on Unix?
(28 answers)
Closed 2 years ago.
I've got a text file given, and the results and the counts vary (date, link and id can be anything). However, the count of dates, links and id's is always the same (so n - n - n for any positive integer n). Is n a positive integer, then the lines n, (n + k/3) and (n+2(k/3)), where k is the number of all lines, belong together.
As en example, I picked out n=3. So lines (1 | 4 | 7), (2 | 5 | 8) and (3 | 6 | 9) belong together:
Today, 17:09
Yesterday, 09:44
08.09.2020
07.09.2020
06.09.2020
/s-show/Link111...
/s-show/Link211...
/s-show/Link311...
/s-show/Link411...
/s-show/Link511...
id="1222222222"
id="2222222222"
id="3222222222"
id="4222222222"
id="5222222222"
I would like to sort the text file as the following:
id="1222222222"Today, 17:09/s-show/Link111...
id="2222222222"Yesterday, 09:44/s-show/Link211
id="3222222222"08.09.2020/s-show/Link311
id="4222222222"07.09.2020/s-show/Link411
id="5222222222"06.09.2020/s-show/Link511
In a former question, I only had two categories (date and link) and was adviced to do it like the following:
lc=$(wc -l <Textfile); paste -d '' <(head -n $((lc/2)) Textfile) <(tail -n
$((lc/2)) Textfile)
However, here I have 3 categories and the head and tail command won't let me read only the lines in the middle.
How could this be solved?
Leveraging the techniques taught in How can I extract a predetermined range of lines from a text file on Unix? --
#!/usr/bin/env bash
input=$1
total_lines=$(wc -l <"$1")
sections=$2
lines_per_section=$(( total_lines / sections ))
if (( lines_per_section * sections != total_lines )); then
echo "ERROR: ${total_lines} does not evenly divide into ${sections} sections" >&2
exit 1
fi
start=0
ranges=( )
for (( i=0; i<sections; i++ )); do
ranges+=( "$start:$(( start + lines_per_section ))" )
(( start += lines_per_section ))
done
get_range() { sed -n "$(( $1 + 1 )),$(( $2 ))p;$(( $2 + 1 ))q" <"$input"; }
consolidate_input() {
if (( $# )); then
current=$1; shift
paste <(get_range "${current%:*}" "${current#*:}") <(consolidate_input "$#")
fi
}
consolidate_input "${ranges[#]}"
But don't do that. Just put your three sections in three separate files, so you can use paste file1 file2 file3.
I have 2 scripts, #1 and #2. Each work OK by themselves. I want to read a 15 row file, row by row, and process it. Script #2 selects rows. Row 0 is is indicated as firstline=0, lastline=1. Row 14 would be firstline=14, lastline=15. I see good results from echo. I want to do the same with script #1. Can't get my head around nesting correctly. Code below.
#!/bin/bash
# script 1
filename=slash
firstline=0
lastline=1
i=0
exec <${filename}
while read ; do
i=$(( $i + 1 ))
if [ "$i" -ge "${firstline}" ] ; then
if [ "$i" -gt "${lastline}" ] ; then
break
else
echo "${REPLY}" > slash1
fold -w 21 -s slash1 > news1
sleep 5
fi
fi
done
# script2
firstline=(0 1 2 3 4 5 6 7 8 9 10 11 12 13 14)
lastline=(1 2 3 4 5 6 7 8 9 10 11 12 13 14 15)
for ((i=0;i<${#firstline[#]};i++))
do
echo ${firstline[$i]} ${lastline[$i]};
done
Your question is very unclear, but perhaps you are simply looking for some simple function calls:
#!/bin/bash
script_1() {
filename=slash
firstline=$1
lastline=$2
i=0
exec <${filename}
while read ; do
i=$(( $i + 1 ))
if [ "$i" -ge "${firstline}" ] ; then
if [ "$i" -gt "${lastline}" ] ; then
break
else
echo "${REPLY}" > slash1
fold -w 21 -s slash1 > news1
sleep 5
fi
fi
done
}
# script2
firstline=(0 1 2 3 4 5 6 7 8 9 10 11 12 13 14)
lastline=(1 2 3 4 5 6 7 8 9 10 11 12 13 14 15)
for ((i=0;i<${#firstline[#]};i++))
do
script_1 ${firstline[$i]} ${lastline[$i]};
done
Note that reading the file this way is extremely inefficient, and there are undoubtedly better ways to handle this, but I am trying to minimize the changes from your code.
Update: Based on your later comments, the following idiomatic Bash code that uses sed to extract the line of interest in each iteration solves your problem much more simply:
Note:
- If the input file does not change between loop iterations, and the input file is small enough (as it is in the case at hand), it's more efficient to buffer the file contents in a variable up front, as is demonstrated in the original answer below.
- As tripleee points out in a comment: If simply reading the input lines sequentially is sufficient (as opposed to extracting lines by specific line numbers, then a single, simple while read -r line; do ... # fold and output, then sleep ... done < "$filename" is enough.
# Determine the input filename.
filename='slash'
# Count its number of lines.
lineCount=$(wc -l < "$filename")
# Loop over the line numbers of the file.
for (( lineNum = 1; lineNum <= lineCount; ++lineNum )); do
# Use `sed` to extract the line with the line number at hand,
# reformat it, and output to the target file.
fold -w 21 -s <(sed -n "$lineNum {p;q;}" "$filename") > 'news1'
sleep 5
done
A simplified version of what I think you're trying to achieve:
#!/bin/bash
# Split fields by newlines on input,
# and separate array items by newlines on output.
IFS=$'\n'
# Read all input lines up front, into array ${lines[#]}
# In terms of your code, you'd use
# read -d '' -ra lines < "$filename"
read -d '' -ra lines <<<$'line 1\nline 2\nline 3\nline 4\nline 5\nline 6\nline 7\nline 8\nline 9\nline 10\nline 11\nline 12\nline 13\nline 14\nline 15'
# Define the arrays specifying the line ranges to select.
firstline=(0 1 2 3 4 5 6 7 8 9 10 11 12 13 14)
lastline=(1 2 3 4 5 6 7 8 9 10 11 12 13 14 15)
# Loop over the ranges and select a range of lines in each iteration.
for ((i=0; i<${#firstline[#]}; i++)); do
extractedLines="${lines[*]: ${firstline[i]}: 1 + ${lastline[i]} - ${firstline[i]}}"
# Process the extracted lines.
# In terms of your code, the `> slash1` and `fold ...` commands would go here.
echo "$extractedLines"
echo '------'
done
Note:
The name of the array variable filled with read -ra is lines; ${lines[#]} is Bash syntax for returning all array elements as separate words (${lines[*]} also refers to all elements, but with slightly different semantics), and this syntax is used in the comments to illustrate that lines is indeed an array variable (note that if you were to use simply $lines to reference the variable, you'd implicitly get only the item with index 0, which is the same as: ${lines[0]}.
<<<$'line 1\n...' uses a here-string (<<<) to read an ad-hoc sample document (expressed as an ANSI C-quoted string ($'...')) in the interest of making my example code self-contained.
As stated in the comment, you'd read from $filename instead:
read -d '' -ra lines <"$filename"
extractedLines="${lines[*]: ${firstline[i]}: 1 + ${lastline[i]} - ${firstline[i]}}" extracts the lines of interest; ${firstline[i]} references the current element (index i) from array ${firstline[#]}; since the last token in Bash's array-slicing syntax
(${lines[*]: <startIndex>: <elementCount>}) is the count of elements to return, we must perform a calculation to determine the count, which is what 1 + ${lastline[i]} - ${firstline[i]} does.
By virtue of using "${lines[*]...}" rather than "${lines[#]...}", the extracted array elements are joined by the first character in $IFS, which in our case is a newline ($'\n') (when extracting a single line, that doesn't really matter).
I'm trying to write a bash script that calculates the average of numbers by rows and columns. An example of a text file that I'm reading in is:
1 2 3 4 5
4 6 7 8 0
There is an unknown number of rows and unknown number of columns. Currently, I'm just trying to sum each row with a while loop. The desired output is:
1 2 3 4 5 Sum = 15
4 6 7 8 0 Sum = 25
And so on and so forth with each row. Currently this is the code I have:
while read i
do
echo "num: $i"
(( sum=$sum+$i ))
echo "sum: $sum"
done < $2
To call the program it's stats -r test_file. "-r" indicates rows--I haven't started columns quite yet. My current code actually just takes the first number of each column and adds them together and then the rest of the numbers error out as a syntax error. It says the error comes from like 16, which is the (( sum=$sum+$i )) line but I honestly can't figure out what the problem is. I should tell you I'm extremely new to bash scripting and I have googled and searched high and low for the answer for this and can't find it. Any help is greatly appreciated.
You are reading the file line by line, and summing line is not an arithmetic operation. Try this:
while read i
do
sum=0
for num in $i
do
sum=$(($sum + $num))
done
echo "$i Sum: $sum"
done < $2
just split each number from every line using for loop. I hope this helps.
Another non bash way (con: OP asked for bash, pro: does not depend on bashisms, works with floats).
awk '{c=0;for(i=1;i<=NF;++i){c+=$i};print $0, "Sum:", c}'
Another way (not a pure bash):
while read line
do
sum=$(sed 's/[ ]\+/+/g' <<< "$line" | bc -q)
echo "$line Sum = $sum"
done < filename
Using the numsum -r util covers the row addition, but the output format needs a little glue, by inefficiently paste-ing a few utils:
paste "$2" \
<(yes "Sum =" | head -$(wc -l < "$2") ) \
<(numsum -r "$2")
Output:
1 2 3 4 5 Sum = 15
4 6 7 8 0 Sum = 25
Note -- to run the above line on a given file foo, first initialize $2 like so:
set -- "" foo
paste "$2" <(yes "Sum =" | head -$(wc -l < "$2") ) <(numsum -r "$2")