Shell Bash Script - linux

I am making a bash script. I have to get 3 variables
VAR1=$(cat /path to my file/ | grep "string1" | awk '{ print $2 }'
VAR2=$(cat /path to my file/ | grep "string2" | awk '{ print $2 }'
VAR3=$(cat /path to my file/ | grep "string3" | awk '{ print $4 }'
My problem is that if I write
echo $VAR1
echo $VAR2
echo $VAR3
I can see values correctly
But when I try to write them in one line like this
echo "VAR1: $VAR1 VAR2: $VAR2 VAR3: $VAR3"
Value from $VAR3 is written at the beginning of output overwritting values of $VAR1 and $VAR2
I expect my explanation had been clear. Any doubt please let me know
Thanks and regards.
Rambert

It seems to me that $VAR3 contains \r which in some shells will move the cursor to the beginning of the line. Use printf instead:
printf "VAR1: %s VAR2: %s VAR3: %s\n" "$VAR1" "$VAR2" "$VAR3"
Also note that the way you extract the values is highly inefficient and can be reduced to one call to awk:
read -r var1 var2 var3 _ < <(awk '/string1/ { a=$2 }
/string2/ { b=$2 }
/string3/ { c=$4 }
END { print(a, b, c) }' /path/to/file)
printf "VAR1: %s VAR2: %s VAR3: %s\n" "$var1" "$var2" "$var3"
A nitpick is that uppercase variable names are reserved for environment variables, so I changed all to lowercase.
<(...) is a process substitution and will make ... write to a "file" and return the file name:
$ echo <(ls)
/dev/fd/63
And command < file is a redirection changing standard input of command to be comming from the file file.

You could write :
cat /path to my file/ | grep "string1" | awk '{ print $2 }'
as
awk '/string1/{print $2}' /path/to/file
In other words you could do with awk alone what you intended to do with cat, grep & awk
So finally get :
VAR1=$(awk '/string1/{print $2}' /path/to/file) #mind the closing ')'
Regarding the issue you face, it looks like you have carriage returns or \r in your variables. In bash echo will not interpret escape sequences without the -e option, but the printf option which [ #andlrc ] pointed out is a good try though as he mentioned in his [ answer ]
which in some shells will move the cursor to the beginning
Notes :
Another subtle point to keep in mind is to avoid using upper case variable names like VAR1 for user scripts. So replace it with var1 or so
When assigning values to variable spaces are not allowed around =, so
VAR1="Note there are no spaces around = sign"
is the right usage

Related

Hex compare in bash scripting

I am facing some issue when I am reading the 3rd word(a hex string) of each line in a text file and compare it with a hex number. Can some one please help me on it.
#!/bin/bash
A=$1
cat $A | while read a; do
a1=$(echo \""$a"\" | awk '{ print $3 }')
#echo $a > cut -d " " -f 3
echo $a1
(("$a1" == 0x10F7))
echo $?
done
But when I use below, the comparison happens correctly,
a1= 0xADCAFE
(( "$a1" == 0x10F7 ))
echo $?
Then why it is showing issue when I read like below,
a1=$(echo \""$a"\" | awk '{ print $3 }')
or> a1=$(echo $a | awk '{ print $3 }')
echo $a prints intended hex value, but comparison does not happen.
Regards,
Running Awk inside a while read loop is an antipattern. Just do the loop in Awk; it's good at that.
awk '$3 == 4343' "$1"
If you want to compare against a string whose value is "0x10F7" then it's
awk '$3 == "0x10F7"' "$1"
If you want to match either, case insensitively etc, a regex is a good way to do that.
awk '$3 ~ /^(0x10[Ff]7|4343)$/' "$1"
Notice how the $1 in double quotes is handled by the shell, and gets replaced by a (properly quoted!) copy of the script's first command-line argument before Awk runs, while the Awk script in single quotes has its own namespace, so $3 is an Awk variable which refers to the third field in the current input line.
Either way, avoid the useless use of cat and always always always quote variables which contain file names with double quotes.
That's literal double quotes. You seem to have tried both a dangerous bare $a and a doubly double-quoted "\"$a\"" where the simple "$a" would be what you actually want.
Thank you all for your responses, Now my script is working fine. I was trying to match two files, below script does the purpose
#!/bin/bash
A=$1
B=$2
dos2unix -f "$A"
dos2unix -f "$B"
rm search_match.txt search_data_match.txt search_nomatch.txt search_data_nomatch.txt
while read line;do
search_word=$(echo $line | awk '{ print $1 }')
grep "$search_word" $B >> temp_file.txt
while read var;do
file1_hex=$(echo $line | awk '{ print $2 }')
file2_hex=$(echo $var | awk '{ print $3 }')
(("$file1_hex" == "$file2_hex"))
zero=$(echo $?)
if [ "$zero" -eq 0 ] ; then
echo $line >> search_match.txt
echo $var >> search_data_match.txt
else
echo $line >> search_nomatch.txt
echo $var >> search_data_nomatch.txt
fi
done < "temp_file.txt"
rm temp_file.txt
done < "$A"

Bash command rev to reverse delemiters

I am working on a shell script that converts exported Microsoft in-addr.apra.txt files to a more useful format so that i can use it in the future in other products for automation purposes. No i am figuring a problem which (im not a programmer) can not solve in a simple way.
Sample script
x=123.223.224
rev $x
gives me
422.322.321
but i want to have the output as follow:
224.223.123
is there a easy way to do it without rev or putting each group in a variable? Or is there a sample i can use? or maybe i use the wrong tools to do it?
Using awk:
x='123.223.224'
awk 'BEGIN{FS=OFS="."} {for (i=NF; i>=2; i--) printf $i OFS; print $1}' <<< "$x"
224.223.123
Use awk for this!
If your text file always contains three octets, simply use . as separator:
echo $x | awk -F. '{ print $3 "." $2 "." $1 }'
For more complex cases, use internal split():
echo $x | awk '{
n = split($0, a, ".");
for(i = n; i > 1; i--) {
printf "%s.", a[i];
}
print a[1]; }'
In this sample split() will split every line (which is passed as argument $0) using delimiter ., saves resulting array into a and returns length of that array (which is saved to n). Note that unlike C,
split() array indexes are starting with one.
Or python:
python -c "print '.'.join(reversed('$x'.split('.')))"
Here is my script.
#!/bin/sh
value=$1
delim=$2
total_fields=$(echo "$value" | tr -cd $2 | wc -c)
let total_fields=total_fields+1
i=1
reverse_value=""
while [ $total_fields -gt 0 ]; do
cur_value=$(echo "$value" | cut -d${delim} -f${total_fields})
if [ $total_fields -ne 1 ]; then
cur_value="$cur_value${delim}"
fi
#echo "$cur_value"
reverse_value="$reverse_value$cur_value"
#echo "$i --> $reverse_value"
let total_fields=total_fields-1
done
echo "$reverse_value"
Using a few small tools.
tr '.' '\n' <<< "$x" | tac | paste -sd.
224.223.123

bash: a more effective way to search strings in a file and extract part of strings

i have an input file as follow:
some lines with quote and :
AGE:23
some lines with quote and :
NAME:2,0,"My Name Is"
some lines with quote and :
Actually i use this code to extract information from the file:
age="$(cat "$file" | awk -F ':' '/AGE:/ { print $2 }')"
name="$(cat "$file" | awk -F '"' '/NAME:/ { print $2 }' )"
echo "age: $age"
echo "name: $name"
output:
age: 23
name: My Name Is
i'm searching for a better way to do this than running cat and awk two times. i have search to do it in one cat/awk line but can't figure it out, not appropriated in this case? can anyone point me a better way please ?
Thanks in advance
while IFS=: read key value; do
case $key in
AGE) age=$value;;
NAME) name=$(awk -F'"' '{print $2}' <<< "$value");;
esac
done < "$file"
I like #JohnKugelman's approach, but it can be improved: use colon and quote as the field separators:
while IFS=':"' read -ra fields; do
case ${fields[0]} in
AGE) age=${fields[1]} ;;
NAME) [[ ${fields[1]} == "2,0," ]] && name=${fields[2]} ;;
esac
done < file
With awk, I'd write:
read age name < <(
awk -F '[:,]' '
$1 == "AGE" {printf "%s ",$2}
$1 == "NAME" && $2 == 2 && $3 == 0 {printf "%s ",$NF}
END {print ""}
' filename
)
If the data is simple as you have shown in your question. No need to use shell for this , just awk will be more than enough
awk -F '"' '/AGE/{print tolower($0)}/NAME/{print "name:"$2}' input.txt

error bash extracting second column of a matched pattern

I am trying to search for a pattern and from the results i am extracting just the second column. The command works well in command line but not inside a bash script.
#!/bin/bash
set a = grep 'NM_033356' test.txt | awk '{ print $2 }'
echo $a
It doesnt print any output at all.
Input
NM_033356 2
NM_033356 5
NM_033356 7
Your code:
#!/bin/bash
set a = grep 'NM_033356' test.txt | awk '{ print $2 }'
echo $a
Change it to:
#!/bin/bash
a="$(awk '$1=="NM_033356"{ print $2 }' test.txt)"
echo "$a"
Code changes are based on your sample input.
.......
a="$(awk '/NM_033356/ { print $2 }' test.txt)"
Try this:
a=`grep 'NM_033356' test.txt | awk '{ print $2 }'`

awk - backticks in solaris to accept command line arg

I have this script that is meant to trim the field specified as argument to the script.
ie sh script.sh file.txt "|" 2
#!/bin/bash
filename="$1"
delim="$2"
arg="$3"
gsubber="\"gsub("^[ \t]*|[ \t]*$","",'\$$arg')\""
myout=`nawk -F"$delim" -v fl="$gsubber" \'{ { fl } }1\' OFS="$delim" "$filename"`
echo "$myout"
So this file 'file.txt' as input:
sid|storeNo|latitude
9| gerdy| fd¿kjhn422-405
0000543210 |gfdjk39
gfd|fd||fd
becomes this output:
sid|storeNo|latitude
9|gerdy| fd¿kjhn422-405
0000543210 |gfdjk39
gfd|fd||fd
I get this error:
nawk: syntax error at source line 1
context is
' <<<
missing }
nawk: bailing out at source line 1
Once someone can assist with providing the correct syntax, I should have no trouble extending it to support multiple fields. ie sh script.sh file.txt "|" 2 3 could then trim the 2nd and 3rd field only.
Thanks in advance!
Try:
#!/bin/bash
filename=$1
delim=$2
arg=$3
regex='^[ \t]*|[ \t]*$'
myout=$(
nawk -F"$delim" -v regex="$regex" -v arg="$arg" '
{ gsub(regex, "", $arg) }
1' OFS="$delim" "$filename"
)
printf '%s\n' "$myout"
Edit:
In order to handle multiple fields in the arguments (see comments below):
#!/bin/bash
filename=$1
delim=$2
shift 2
args=$#
regex='^[ \t]*|[ \t]*$'
myout=$(
nawk -F"$delim" -v regex="$regex" -v args="$args" '{
n = split(args, t, " ")
for (i = 0; ++i <=n;)
gsub(regex, "", $t[i])
}1' OFS="$delim" "$filename"
)
printf '%s\n' "$myout"
this should work:
#!/bin/bash
filename="$1"
delim="$2"
arg="$3"
myout=`nawk -F"$delim" -v f="$arg" '{gsub(/^[ \t]*|[ \t]*$/,"",$f) }1' OFS="$delim" "$filename"`
echo "$myout"
you don't have to extract gsub out, since in the gsub function call, only field index is variable. you could pass the field index as var to awk.

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