I am new to shell scripting. I need to read a file that works in all shells that has variables defined in it. Something like:
variable1=test1
variable2=test2
....
I have to read this file line by line and prepare new string separated by spaces, like:
variable=variable1=test1 variable2=test2 ....
I tried with the below code:
while read LINE
do
$VAR="$VAR $LINE"
done < test.dat
but it's throwing me this error:
command not found Test.sh: line 3: = variable1=test1
The problem with your script is the leading $ before var is initialized, try:
#/bin/bash
while read line; do
var="$var $line"
done < file
echo "$var"
However you can do this with the tr command by substituting the newline character with a space.
$ tr '\n' ' ' < file
variable1=test1 variable2=test2
$ var="$(tr '\n' ' ' < file)"
$ echo "$var"
variable1=test1 variable2=test2
When defining a shell variable you must omit the $. So VAR="bla" is right, $VAR="bla" is wrong. The $ is only necessary for using the variable, as in echo $VAR;
while read LINE
do
VAR="$VAR $LINE"
done < test.dat
Related
I have read the config file which has the below variable:
export BASE_DIR="\usr\usr1"
In the same script I read a file line by line and I wanted to substitute the ${BASE_DIR} with \usr\usr1.
In the script:
while read line; do
echo $line
done <file.txt
${BASE_DIR}\path1 should be printed as \usr\usr1\path1
Tried eval echo and $(( )).
Can use sed, This command will search and replace a value. The dollar sign is the separator.
sed -ie 's$\${BASE_DIR}$\\usr\\usr1$1' hello.txt
You need to set the variable when you read the line that contains the assignment. Then you can replace it later.
#!/bin/bash
while read line; do
if [[ $line =~ ^BASE_DIR= ]]
then basedir=${line#BASE_DIR=}
fi
line=${line/'${BASE_DIR}'/$basedir}
printf "%s\n" "$line"
done < file.txt > newfile.txt
In bash script, how can I read the file line by line and assign to the variable with delimiter?
example.txt file contents:
string1
string2
string3
string4
Expected output:
string1,string2,string3,string4
Thanks in advance
Apparently my answer below leaves a comma at the end of the line. A quick workaround is to use the following builtin in Unix:
paste -sd, example.txt
Where you use the paste program to concatenate all the lines into one and then add the string delimiter ','
Using the builtin commands in unix:
tr '\n' ',' < example.txt
This can be broken down as truncating all Newline widcards and inserting a comma delimiter instead.
Other possible ways, just for fun:
mapfile -t a < example.txt
(IFS=,; echo "${a[*]}")
mapfile -t a < example.txt
foo=$(printf '%s' "${a[#]/%/,}")
echo "${foo%,}"
foo=$(<example.txt)
echo "${foo//$'\n'/,}"
{
IFS= read -r foo
while IFS= read -r line; do
foo+=,$line
done
} < example.txt
echo "$foo"
sed ':a;N;$!ba;s/\n/,/g' example.txt
It should work:
#!/bin/bash
output=''
while IFS='' read -r line || [[ -n "$line" ]]; do
output=$output:",$line"
done < "$1"
echo $output
Give the file as argument
This is my code to read a file line by line:
IFS=$'\n'
myfile="$1"
i=0
while read line; do
echo "Line # $i: '$line'"
let i++
done < "$myfile"
This is the file passed as parameter
Hello
stack
overflow
friends
I execute it like this: test.sh input.txt and I get this result:
'ine # 0: 'Hello
'ine # 1: 'stack
'ine # 2: 'overflow
'ine # 3: 'friends
As you see, The fisrt character is replaced by a quote. And the quote of the final of the line does not appear. Whats going on here? I can't see the mistake? Any idea?
Most likely you have \r before end of line in your input file.
You can test same by using:
cat -vte file
This will show ^M$ in the end of file has dos carriage return \r.
You can use this script to read your file correctly:
i=1
while IFS=$'\r' read -r line; do
echo "Line # $i: '$line'"
let i++
done < "$myfile"
OR else convert your file into unix file using:
dos2unix file
OR If you don't wish to actually save the file stripped off of \r, you can also use:
while read line; do
........# your code as-is
done < <( tr -d '\r' < "$myfile")
I am trying to remove newlines from a file. My file is like this (it contains backward slashes):
line1\|
line2\|
I am using the following script to remove newlines:
#!/bin/bash
INPUT="file1"
while read line
do
: echo -n $line
done < $INPUT
I get the following output:
line1|line2|
It removes the backslashes. How can I retain those backslashes?
The -r option to read prevents backslash processing of the input.
while read -r line
do
echo -n "$line"
done < $INPUT
But if you just want to remove all newlines from the input, the tr command would be better:
tr -d '\n' < $INPUT
Try sed 's/\n//' /path/to/file
i am trying to read a text file, say file.txt and it contains multiple lines.
say the output of file.txt is
$ cat file.txt
this is line 1
this is line 2
this is line 3
I want to store the entire output as a variable say, $text.
When the variable $text is echoed, the expected output is:
this is line 1 this is line 2 this is line 3
my code is as follows
while read line
do
test="${LINE}"
done < file.txt
echo $test
the output i get is always only the last line. Is there a way to concatenate the multiple lines in file.txt as one long string?
You can translate the \n(newline) to (space):
$ text=$(tr '\n' ' ' <file.txt)
$ echo $text
this is line 1 this is line 2 this is line 3
If lines ends with \r\n, you can do this:
$ text=$(tr -d '\r' <file.txt | tr '\n' ' ')
Another one:
line=$(< file.txt)
line=${line//$'\n'/ }
test=$(cat file.txt | xargs)
echo $test
You have to append the content of the next line to your variable:
while read line
do
test="${test} ${LINE}"
done < file.txt
echo $test
Resp. even simpler you could simply read the full file at once into the variable:
test=$(cat file.txt)
resp.
test=$(tr "\n" " " < file.txt)
If you would want to keep the newlines it would be as simple as:
test=<file.txt
I believe it's the simplest method:
text=$(echo $(cat FILE))
But it doesn't preserve multiple spaces/tabs between words.
Use arrays
#!/bin/bash
while read line
do
a=( "${a[#]}" "$line" )
done < file.txt
echo -n "${a[#]}"
output:
this is line 1 this is line 2 this is line 3
See e.g. tldp section on arrays