I am using Linux and bash.
I have a simple text file like below:
VAR1=100
VAR2=5
VAR3=0
VAR4=99
I want to extract by means of bash the value of VAR2, that is 5.
How could I do that?
Assuming the file is called vars.txt
sed -n 's/^VAR2=\(.*\)/\1/p' < vars.txt
You can use the value elsewhere like this using single back quotes
echo VAR2=`sed -n 's/^VAR2=\(.*\)/\1/p' < txt`
The simplest way might be to use source or simply . to read and execute the file. This would work with your example, because there are no spaces in the variable values. Otherwise you need to use grep + cut or awk, as stated in other answers.
. /path/to/your/file
echo $VAR2
[edit]
As stated by dawg, this would make the other variables available in your script too, and possibly overwrite existing variables.
Given:
$ echo "$txt"
VAR1=100
VAR2=5
VAR3=0
VAR4=99
You can use awk:
$ echo "$txt" | awk -F= '/^VAR2/ { print $2 }'
5
Or grep and cut:
$ echo "$txt" | egrep '^VAR2=\d+' | cut -d = -f 2
5
On Bash, you can insert the value of those assignments into the current shell using source and filter the lines you wish to use. In this case, only the line VAR2=5 will be used. You need to write that to a file and then source that file:
$ echo "$txt" | grep '^VAR2' > tmp && source tmp && rm tmp
$ echo $VAR2
5
For the files as described, you can just source the file as bash script which will run it's content and update you workspace environment with it. For example:
source file.txt
echo $VAR2
Assume this as your txt file, named test.txt
VAR2 = 5
VAR3 = 0
VAR4 = 99
you can cat test.txt | grep 'VAR2' | awk '{printf $3}'
and then your output will be: 5
Here, cat test.txt will display the content of test.txt in your terminal,grep 'VAR2' will list lines containing 'VAR2' and awk '{printf $3}' will print the value of the variable
Related
I have a file that looks like:
>ref_frame=1
TPGIRYQYNVLPQGWKGSPAIFQSSMTKILEPFRKQNPDIVIYQYMDDLYVGSD
>ref_frame=2
HQGLDISTMCFHRDGKDHQQYSKVA*QKS*SLLENKIQT*LSINTWMICM*DLT
>ref_frame=3
TRD*ISVQCASTGMERITSNIPK*HDKNLRAF*KTKSRHSYLSIHG*FVCRI*
>test_3_2960_3_frame=1
TPGIRYQYNVLPQGWKGSPAIFQSSMTKILEPSRKQNPDIVIYQYMDDLYVGSD
I want to assign a bash variable so that echo $variable gives test_3_2960
The line/row that I want to assign the variable to will always be line 7. How can I accomplish this using bash?
so far I have:
variable=`cat file.txt | awk 'NR==7'`
echo $variable = >test_3_2960_3_frame=1
Using sed
$ variable=$(sed -En '7s/>(([^_]*_){2}[0-9]+).*/\1/p' input_file)
$ echo "$variable"
test_3_2960
No pipes needed here...
$: variable=$(awk -F'[>_]' 'NR==7{ OFS="_"; print $2, $3, $4; exit; }' file)
$: echo $variable
test_3_2960
-F is using either > or _ as field separators, so your data starts in field 2.
OFS="_" sets the Output Field Separator, but you could also just use "_" instead of commas.
exit keeps it from wasting time bothering to read beyond line 7.
If you wish to continue with awk
$ variable=$(awk 'NR==7' file.txt | awk -F "[>_]" '{print $2"_"$3"_"$4}')
$ echo $variable
test_3_2960
I have a file with the following content:
"X-Apple-I-MD-M" = "MR7v7ctwW0yr3mAUY3rAluXgOReA4CIn1JWJS2ba1s";
I want to extract the returned results Output as:
MR7v7ctwW0yr3mAUY3rAluXgOReA4CIn1JWJS2ba1s
Tks Everybody!
One awk idea, assuming this is the only line in the file:
$ awk -F'"' '{print $4}' file
MR7v7ctwW0yr3mAUY3rAluXgOReA4CIn1JWJS2ba1s
If there are other lines and you wish to focus only on the line with the string "X-Apple-I-MD-M":
Input file:
$ cat file
some line to ignore
"X-Apple-I-MD-M" = "MR7v7ctwW0yr3mAUY3rAluXgOReA4CIn1JWJS2ba1s";
other line to ignore and "with" some "quotes"
New awk idea:
$ pattern='X-Apple-I-MD-M'
$ awk -v ptn="${pattern}" -F'"' '$2==ptn {print $4}' file
MR7v7ctwW0yr3mAUY3rAluXgOReA4CIn1JWJS2ba1s
And saving the awk result in a variable:
$ mystring=$(awk ... )
$ echo "${mystring}"
MR7v7ctwW0yr3mAUY3rAluXgOReA4CIn1JWJS2ba1s
NOTE: keep in mind if there are multiple matching lines in file then ${mystring} will contain a multi-line value (eg, line1match\nline2match\nline3match
I always like sed.
$: echo '"X-Apple-I-MD-M" = "MR7v7ctwW0yr3mAUY3rAluXgOReA4CIn1JWJS2ba1s";'| sed -E 's/^.*= *"([^"]+)" *; *$/\1/'
MR7v7ctwW0yr3mAUY3rAluXgOReA4CIn1JWJS2ba1s
if it's a file,
$: sed -E 's/^.*= *"([^"]+)" *; *$/\1/' file
MR7v7ctwW0yr3mAUY3rAluXgOReA4CIn1JWJS2ba1s
With GNU grep(1), something like.
grep -Po '(?<="X-Apple-I-MD-M" = ").*(?=";)' <<< '"X-Apple-I-MD-M" = "MR7v7ctwW0yr3mAUY3rAluXgOReA4CIn1JWJS2ba1s";'
If it is in a file.
grep -Po '(?<="X-Apple-I-MD-M" = ").*(?=";)' file.txt
If your content is consistent, an ugly solution is:
VAL='"X-Apple-I-MD-M" = "MR7v7ctwW0yr3mAUY3rAluXgOReA4CIn1JWJS2ba1s";'
echo $VAL
echo $VAL | awk '{split($0, a, " = "); print(substr(a[2], 2, length(a[2]) - 3))}'
Guessing by the bash tag, this is probably supposed to be in pure Bash, without external processes…? Two (somewhat) random options:
while IFS='"' read _ _ _ code _; do
echo "$code"
done
while read line; do
line="${line#\"*\" = \"}"
line="${line%\";}"
echo "$line"
done
I have a file in the directory with this text
VERSION_NUMBER: 1
I need to get the value of VERSION_NUMBER convert it to number and make n+1 and write it to a variable, for example variable test.
How I can do this using sed
Assumptions:
there's only one line in the input file
there's no need to verify that the value following the : is a number
no need to update the file with the new value
Input file:
$ cat myfile
VERSION_NUMBER: 1
One sed idea:
$ x=$(sed -En 's/^.*: (.*)$/\1/p' myfile)
$ ((x++))
$ echo "${x}"
2
One cut idea:
$ x=$(cut -d: -f2 myfile)
$ ((x++))
$ echo "${x}"
2
Same thing with awk:
$ x=$(awk '{print $2}' myfile)
$ ((x++))
$ echo "${x}"
2
In a comment OP has asked how to update the file with the new value.
Since we're only talking about a single line the following ...
$ echo "VERSION_NUMBER: ${x}" > myfile
... is probably going to be easier/simpler than running another sed or awk command to overwrite the current file.
I need to read a file that has lines like
user=username1
pass=password1
How can I read multiple lines like this into separate variables like username and password?
Would I use awk or grep? I have found ways to read lines into variables with grep but would I need to read the file for each individual item?
The end result is to use these variables to access a database via the command line. So I need to be able to read, store and use these values in other commands.
if the process which generates the file is safe and has shell syntax just source the file.
. ./file
Otherwise the file can be processes before to add quotes
perl -ne 'if (/^([A-Za-z_]\w*)=(.*)/) {$k=$1;$v=$2;$v=~s/\x27/\x27\\\x27\x27/g;print "$k=\x27$v\x27\n";}' <file >file2
. ./file2
If you want to use awk then
Input
$ cat file
user=username1
pass=password1
Reading
$ user=$(awk -F= '$1=="user"{print $2;exit}' file)
$ pass=$(awk -F= '$1=="pass"{print $2;exit}' file)
Output
$ echo $user
username1
$ echo $pass
password1
You could use a loop for your file perhaps, but this is probably the functionality you're looking for.
$ echo 'user=username1' | awk -F= '{print $2}'
username1
Using the -F flag sets the delimiter to = and we select the 2nd item from the row.
file.txt:
user=username1
pass=password1
user=username2
pass=password2
user=username3
pass=password3
Do to avoid browsing several times the file file.txt:
#!/usr/bin/env bash
func () {
echo "user:$1 pass:$2"
}
i=0
while IFS='' read -r line; do
if [ $i -eq 0 ]; then
i=1
user=$(echo ${line} | cut -f2 -d'=')
else
i=0
pass=$(echo ${line} | cut -f2 -d'=')
func "$user" "$pass"
fi
done < file.txt
Output:
user:username1 pass:password1
user:username2 pass:password2
user:username3 pass:password3
I would like to use the lines coming from 'wc' as variables. For example:
echo 'foo bar' > file.txt
echo 'blah blah blah' >> file.txt
wc file.txt
2 5 23 file.txt
I would like to have something like $lines, $words and $characters associated to the values 2, 5, and 23. How can I do that in bash?
In pure bash: (no awk)
a=($(wc file.txt))
lines=${a[0]}
words=${a[1]}
chars=${a[2]}
This works by using bash's arrays. a=(1 2 3) creates an array with elements 1, 2 and 3. We can then access separate elements with the ${a[indice]} syntax.
Alternative: (based on gonvaled solution)
read lines words chars <<< $(wc x)
Or in sh:
a=$(wc file.txt)
lines=$(echo $a|cut -d' ' -f1)
words=$(echo $a|cut -d' ' -f2)
chars=$(echo $a|cut -d' ' -f3)
There are other solutions but a simple one which I usually use is to put the output of wc in a temporary file, and then read from there:
wc file.txt > xxx
read lines words characters filename < xxx
echo "lines=$lines words=$words characters=$characters filename=$filename"
lines=2 words=5 characters=23 filename=file.txt
The advantage of this method is that you do not need to create several awk processes, one for each variable. The disadvantage is that you need a temporary file, which you should delete afterwards.
Be careful: this does not work:
wc file.txt | read lines words characters filename
The problem is that piping to read creates another process, and the variables are updated there, so they are not accessible in the calling shell.
Edit: adding solution by arnaud576875:
read lines words chars filename <<< $(wc x)
Works without writing to a file (and do not have pipe problem). It is bash specific.
From the bash manual:
Here Strings
A variant of here documents, the format is:
<<<word
The word is expanded and supplied to the command on its standard input.
The key is the "word is expanded" bit.
lines=`wc file.txt | awk '{print $1}'`
words=`wc file.txt | awk '{print $2}'`
...
you can also store the wc result somewhere first.. and then parse it.. if you're picky about performance :)
Just to add another variant --
set -- `wc file.txt`
chars=$1
words=$2
lines=$3
This obviously clobbers $* and related variables. Unlike some of the other solutions here, it is portable to other Bourne shells.
I wanted to store the number of csv file in a variable. The following worked for me:
CSV_COUNT=$(ls ./pathToSubdirectory | grep ".csv" | wc -l | xargs)
xargs removes the whitespace from the wc command
I ran this bash script not in the same folder as the csv files. Thus, the pathToSubdirectory
You can assign output to a variable by opening a sub shell:
$ x=$(wc some-file)
$ echo $x
1 6 60 some-file
Now, in order to get the separate variables, the simplest option is to use awk:
$ x=$(wc some-file | awk '{print $1}')
$ echo $x
1
declare -a result
result=( $(wc < file.txt) )
lines=${result[0]}
words=${result[1]}
characters=${result[2]}
echo "Lines: $lines, Words: $words, Characters: $characters"