This question already has answers here:
Creating an array from a text file in Bash
(7 answers)
Closed 6 years ago.
I'm trying to read numbers from .txt file and than store it into array so I can sort them using bubble sort.
I was trying something like that:
input=$1
readIt=`cat $1`
array=${#readIt[*]}
When I was trying to display it using echo it is displaying good, but when I'm trying to sort it, then it doesn't work.
Any help, please?
EDIT: I checked other topics, but I want to solve this problem using "cat" to understand it in easier way as beginner.
Use readarray (bash 4+)
readarray -t array < "$1"
or a loop (prior to bash 4):
while IFS= read -r line; do
array+=("$line")
done < "$1"
Related
This question already has answers here:
Do not show results if directory is empty using Bash
(3 answers)
Closed 4 years ago.
So I have to find all the files in the directory that start with the letter a, and list them out. This is pretty easy by doing
cd some_directory
for file in a*; do
echo "$file"
done
However I want that if there are no files present that match a*, then the for loop will not run at all. Currently, if this is the case then the shell will echo
a*
Is there a way to do this? Thank you
Your text is opposite of your title, in my answer below I've assumed the text is your intention and your title is incorrect:
globs can be made to act like this with the bash shell option "nullglob":
shopt -s nullglob
An alternative is to use find and ignore errors by piping stderr to /dev/null
for file in $(find a* 2>/dev/null); do
echo "$file"
done
This question already has answers here:
Variables overwriting text problem with "echo" in Bash
(2 answers)
Closed 4 years ago.
I wrote a script to change .CSV to json.
#!/bin/bash
exec 0< example.csv
while IFS=, read name element input decrease
do
echo "${element}decrease: ${decrease}test"
done
the example.csv I paste here
name1,A,11,12
name2,B,13,14
But the output is really weird...
testrease: 12
testrease: 14
As u can see, The test rewrite Adecrease and Bdecrease, makes them to testrease.
I can't believe it!! So I tried with out exec 0< example.csv, type them in stdin, this time I got what I want
name1,A,11,12
Adecrease: 12test
So I guess maybe there are some characters in example.csv I can't see which makes this problem. I use cat -v example.csv
name1,A,11,12^M
name2,B,13,14^M
Nothing strange and I stuck here.
I am very new to shell script, so if anyone can give me some suggestions I will be really thrilled!!
Thank u, #chepner! tag wiki saves me another hour on this stupid question.
And here is the solution from wiki:
Check whether your script or data has DOS style end-of-line characters.
Use cat -v yourfile or echo "$yourvariable" | cat -v.
DOS carriage returns will show up as ^M after each line.
If you find them, delete them using dos2unix (a.k.a. fromdos) or tr -d '\r'.
This question already has answers here:
How to cat multiple files from a list of files in Bash?
(6 answers)
Closed 4 years ago.
How should i concatenate multiple text files get by arguments in terminal using a script in Bash?
#!/bin/bash
while read $1
do
cat $1 > cat.txt
done
I tried that example but it is not working.
You should use '>>' to concatenate ('>' will create a new file each time):
for file in "$#"
do
cat $file >> result
done
This question already has answers here:
Rename multiple files in bash
(3 answers)
Closed 8 years ago.
The only way I am aware of to do this operation is with a for loop iterating over each file:
for file in *something.txt; do
out=\`echo $file | sed 's/something/else/'\`; mv $file $out;
done
I was wondering if there is any other way or shortcut for it (using GNU bash).
There is also simple substring replacement provided as part of bash itself:
mv $file ${file/something/else}
example:
$ touch {1..3}something.txt
$ ( for i in *something.txt; do mv $i ${i/something/else}; done )
$ ls -1 *else*
1else.txt
2else.txt
3else.txt
There's rename and the same basic loop concept as in your post only in whatever programming language you choose.
This question already has answers here:
Capturing multiple line output into a Bash variable
(7 answers)
Closed 5 years ago.
I'm trying to capture a block of text into a variable, with newlines maintained, then echo it.
However, the newlines don't seemed to be maintained when I am either capturing the text or displaying it.
Any ideas regarding how I can accomplish this?
Example:
#!/bin/bash
read -d '' my_var <<"BLOCK"
this
is
a
test
BLOCK
echo $my_var
Output:
this is a test
Desired output:
this
is
a
test
You need to add " quotes around your variable.
echo "$my_var"