I have pipe-delimited text files that requires an MD5 hash of a particular field, or set of fields. Because I'm on AIX and have to use the csum function, I don't think I can simply pass the file and a hashing function to awk to do it in one fell swoop.
So I'm writing a script that reads through each line, passes the to-be-hashed field to csum, then drops the result back in as a replacement via a gsub. 99% of the time it seems to work OK, but sometimes something goes afoul because the gsub replaces something it shouldn't.
#!/bin/ksh
rm $2 #Get rid of output file
while read line; do #loop through each line
MYFIELD=$(echo "$line" | cut -d "|" -f 6); #push the 6th field into a var
MYHASH=$(echo $MYFIELD | csum -h MD5 -); #csum will hash a string only on the stdin
echo $line | sed -e "s/$MYFIELD/${MYHASH}/g" >> $2 #gsub replaces, but not always what we want
done < $1 #read in the input file
I think instead I could use awk to update the field. But it's beyond me how to do that one line at a time. Ideally I would like to have a script that would allow me to pass two mandatory parameters (infile and outfile) and then any number of field positions that would get hashed and replaced. A la
foo infile.txt outfile.txt 2 6 12
Which would read in infile.txt, hash fields 2, 6, and 12, and write out to outfile.txt.
Your suggestions would be most appreciated
What about doing it with awk?
Instead of
echo $line | sed -e "s/$MYFIELD/${MYHASH}/g" >> $2 #gsub replaces, but not always what we want
You can use
old=$MYFIELD; new=$MYHASH; echo $line | awk -F"|" -v o="$old" -v n="$new" '{OFS=FS} sub(o, n, $6) {print}' >> $2
Basically what we do is:
old=$MYFIELD; new=$MYHASH We assign the parameters to be sent to awk.
echo $line We output the line so that awk can get it.
In awk,
-F"|" define | as field separator.
-v o="$old" and -v n="$new" let awk work with variables $old and $new naming them o and n respectively.
{OFS=FS} - define the delimiter between fields. It could also be OFS="|", but this way we indicate awk to use the same we defined on -F="|". It is more flexible to keep the field separator in case it changes.
sub(o, n, $6) replaces the text on variable o (that is, $MYFIELD) with text on variable v (that is, $MYHASH), but just on field 6.
print the whole line with substituted text
This worked for me in the example you gave on comments:
old="hashit"; new="WE_DID"; echo "donthashit|foo1|bar1|foo2|bar2|hashit" | awk -F"|" -v o="$old" -v n="$new" '{OFS=FS} sub(o,n,$6) {print}'
donthashit|foo1|bar1|foo2|bar2|WE_DID
Hope it helps.
Edit
I found a way to pass variables to awk easily: -v o=${variable_name}
This way, the solution can be:
echo $line | awk -F"|" -v o=${MYFIELD} -v n=${MYHASH} '{OFS=FS} sub(o, n, $6) {print}' >> $2
Related
I found some ways to pass external shell variables to an awk script, but I'm confused about ' and ".
First, I tried with a shell script:
$ v=123test
$ echo $v
123test
$ echo "$v"
123test
Then tried awk:
$ awk 'BEGIN{print "'$v'"}'
$ 123test
$ awk 'BEGIN{print '"$v"'}'
$ 123
Why is the difference?
Lastly I tried this:
$ awk 'BEGIN{print " '$v' "}'
$ 123test
$ awk 'BEGIN{print ' "$v" '}'
awk: cmd. line:1: BEGIN{print
awk: cmd. line:1: ^ unexpected newline or end of string
I'm confused about this.
#Getting shell variables into awk
may be done in several ways. Some are better than others. This should cover most of them. If you have a comment, please leave below. v1.5
Using -v (The best way, most portable)
Use the -v option: (P.S. use a space after -v or it will be less portable. E.g., awk -v var= not awk -vvar=)
variable="line one\nline two"
awk -v var="$variable" 'BEGIN {print var}'
line one
line two
This should be compatible with most awk, and the variable is available in the BEGIN block as well:
If you have multiple variables:
awk -v a="$var1" -v b="$var2" 'BEGIN {print a,b}'
Warning. As Ed Morton writes, escape sequences will be interpreted so \t becomes a real tab and not \t if that is what you search for. Can be solved by using ENVIRON[] or access it via ARGV[]
PS If you have vertical bar or other regexp meta characters as separator like |?( etc, they must be double escaped. Example 3 vertical bars ||| becomes -F'\\|\\|\\|'. You can also use -F"[|][|][|]".
Example on getting data from a program/function inn to awk (here date is used)
awk -v time="$(date +"%F %H:%M" -d '-1 minute')" 'BEGIN {print time}'
Example of testing the contents of a shell variable as a regexp:
awk -v var="$variable" '$0 ~ var{print "found it"}'
Variable after code block
Here we get the variable after the awk code. This will work fine as long as you do not need the variable in the BEGIN block:
variable="line one\nline two"
echo "input data" | awk '{print var}' var="${variable}"
or
awk '{print var}' var="${variable}" file
Adding multiple variables:
awk '{print a,b,$0}' a="$var1" b="$var2" file
In this way we can also set different Field Separator FS for each file.
awk 'some code' FS=',' file1.txt FS=';' file2.ext
Variable after the code block will not work for the BEGIN block:
echo "input data" | awk 'BEGIN {print var}' var="${variable}"
Here-string
Variable can also be added to awk using a here-string from shells that support them (including Bash):
awk '{print $0}' <<< "$variable"
test
This is the same as:
printf '%s' "$variable" | awk '{print $0}'
P.S. this treats the variable as a file input.
ENVIRON input
As TrueY writes, you can use the ENVIRON to print Environment Variables.
Setting a variable before running AWK, you can print it out like this:
X=MyVar
awk 'BEGIN{print ENVIRON["X"],ENVIRON["SHELL"]}'
MyVar /bin/bash
ARGV input
As Steven Penny writes, you can use ARGV to get the data into awk:
v="my data"
awk 'BEGIN {print ARGV[1]}' "$v"
my data
To get the data into the code itself, not just the BEGIN:
v="my data"
echo "test" | awk 'BEGIN{var=ARGV[1];ARGV[1]=""} {print var, $0}' "$v"
my data test
Variable within the code: USE WITH CAUTION
You can use a variable within the awk code, but it's messy and hard to read, and as Charles Duffy points out, this version may also be a victim of code injection. If someone adds bad stuff to the variable, it will be executed as part of the awk code.
This works by extracting the variable within the code, so it becomes a part of it.
If you want to make an awk that changes dynamically with use of variables, you can do it this way, but DO NOT use it for normal variables.
variable="line one\nline two"
awk 'BEGIN {print "'"$variable"'"}'
line one
line two
Here is an example of code injection:
variable='line one\nline two" ; for (i=1;i<=1000;++i) print i"'
awk 'BEGIN {print "'"$variable"'"}'
line one
line two
1
2
3
.
.
1000
You can add lots of commands to awk this way. Even make it crash with non valid commands.
One valid use of this approach, though, is when you want to pass a symbol to awk to be applied to some input, e.g. a simple calculator:
$ calc() { awk -v x="$1" -v z="$3" 'BEGIN{ print x '"$2"' z }'; }
$ calc 2.7 '+' 3.4
6.1
$ calc 2.7 '*' 3.4
9.18
There is no way to do that using an awk variable populated with the value of a shell variable, you NEED the shell variable to expand to become part of the text of the awk script before awk interprets it. (see comment below by Ed M.)
Extra info:
Use of double quote
It's always good to double quote variable "$variable"
If not, multiple lines will be added as a long single line.
Example:
var="Line one
This is line two"
echo $var
Line one This is line two
echo "$var"
Line one
This is line two
Other errors you can get without double quote:
variable="line one\nline two"
awk -v var=$variable 'BEGIN {print var}'
awk: cmd. line:1: one\nline
awk: cmd. line:1: ^ backslash not last character on line
awk: cmd. line:1: one\nline
awk: cmd. line:1: ^ syntax error
And with single quote, it does not expand the value of the variable:
awk -v var='$variable' 'BEGIN {print var}'
$variable
More info about AWK and variables
Read this faq.
It seems that the good-old ENVIRON awk built-in hash is not mentioned at all. An example of its usage:
$ X=Solaris awk 'BEGIN{print ENVIRON["X"], ENVIRON["TERM"]}'
Solaris rxvt
You could pass in the command-line option -v with a variable name (v) and a value (=) of the environment variable ("${v}"):
% awk -vv="${v}" 'BEGIN { print v }'
123test
Or to make it clearer (with far fewer vs):
% environment_variable=123test
% awk -vawk_variable="${environment_variable}" 'BEGIN { print awk_variable }'
123test
You can utilize ARGV:
v=123test
awk 'BEGIN {print ARGV[1]}' "$v"
Note that if you are going to continue into the body, you will need to adjust
ARGC:
awk 'BEGIN {ARGC--} {print ARGV[2], $0}' file "$v"
I just changed #Jotne's answer for "for loop".
for i in `seq 11 20`; do host myserver-$i | awk -v i="$i" '{print "myserver-"i" " $4}'; done
I had to insert date at the beginning of the lines of a log file and it's done like below:
DATE=$(date +"%Y-%m-%d")
awk '{ print "'"$DATE"'", $0; }' /path_to_log_file/log_file.log
It can be redirect to another file to save
Pro Tip
It could come handy to create a function that handles this so you dont have to type everything every time. Using the selected solution we get...
awk_switch_columns() {
cat < /dev/stdin | awk -v a="$1" -v b="$2" " { t = \$a; \$a = \$b; \$b = t; print; } "
}
And use it as...
echo 'a b c d' | awk_switch_columns 2 4
Output:
a d c b
I am trying to unzip files in folder and print first line LASTMODIFIEDDATE
But the below will print First line with '-'
for file in /export/home/xxxxxx/New_folder/*.gz;
do
gzip -dc "$file" | awk 'NR=1 {print $0, FILENAME}' | awk '/LASTMODIFIEDDATE/'
done
1.How can i modify the above code to print filename that is unzipped.
2.I am a beginner and suggestion to improve the above code are welcome
A few issues:
Your first awk should have double equals signs if you mean to address the first line:
awk 'NR==1{...}'
Your second awk will only ever see the output of the first awk, which only shows the first line, so you will not see any lines with LASTMODIFIED in them unless they are the first. So this will show you the first line and any lines containing LASTMODIFIED.
for ...
do
echo $file
gzip -dc "$file" | awk 'NR==1 || /LASTMODIFIED/'
done
Or you may mean this:
for ...
do
gzip -dc "$file" | awk -v file="$file" 'NR==1{print $0 " " file} /LASTMODIFIED/'
done
which will print the first line followed by the filename and also any lines containing LASTMODIFIED.
Do this with an echo. Also you might want to use grep instead of awk in this case.
for file in /export/home/xxxxxx/New_folder/*.gz;
do
echo $file
gzip -dc "$file" | grep LASTMODIFIEDDATE
done
I've always used Stack Overflow to get help with issues but this is my first post. I am new to UNIX scripting and I was given a task to get values of column two and then run a command on them. The command I am suppose to run is 'echo -n "$2" | openssl dgst -sha1;' which is a function to hash a value. My problem is not hashing one value, but hashing them all and then printing them. Can someone maybe help me figure this out? This is how I am starting but I think the path I am going is wrong.
NOTE: this is a CSV text file and I know I need to use AWK command for this.
awk 'BEGIN { FS = "," } ; { print $2 }'
while [ "$2" != 0 ];
do
echo -n "$2" | openssl dgst -sha1
done
This prints the second column in it's entirety and also print some type of hashed value.
Sorry for the long first post, just trying to be as specific as possible. Thanks!
You don't really need awk just for extracting the second column. You can do by using bash read built in and setting the IFS to the delimiter.
while IFS=, read -ra line; do
[[ ${line[1]} != 0 ]] && echo "${line[1]}" | openssl dgst -sha1
done < inputFile
You should probably post some sample input data and the error you are getting so that someone can debug your existing code better.
This will do the trick:
$ awk '{print $2}' file | xargs -n1 openssl dgst -sha1
Use awk to print the second field in the file and xargs with the -n1 to pass each record separately to openssl.
If by CSV you mean each record is seperated by a comma then you need to add -F, to awk.
$ awk -F, '{print $2}' file | xargs -n1 openssl dgst -sha1
i need to take the sum of all the values present at a particular index in every line of a csv file. the file may contain more than 50000 records. so efficiency is a given.
i was trying the following code. but doesnt seem to be working.
#!/bin/sh
FILE=$1
# read $FILE using the file descriptors
exec 3<&0
exec 0<$FILE
while read line
do
valindex=`cut -d "," -f 3`
echo $valindex
sum=`expr $sum+$valindex`
done
echo $sum
You should initialise sum before your while loop:
sum=0
You need to cut the line you are reading:
valindex=`echo $line|cut -d "," -f 3`
You need a space before and after the plus in expr:
sum=`expr $sum + $valindex`
Alternatively, use awk. It's a lot simpler:
awk -F, '{SUM+=$3} END{print SUM}' $FILE
Or one of my favourite patterns:
cut -d "," -f 3 "$FILE" | paste -sd+ | bc
I need to get the records from a text file in Unix. The delimiter is multiple blanks. For example:
2U2133 1239
1290fsdsf 3234
From this, I need to extract
1239
3234
The delimiter for all records will be always 3 blanks.
I need to do this in an unix script(.scr) and write the output to another file or use it as an input to a do-while loop. I tried the below:
while read readline
do
read_int=`echo "$readline"`
cnt_exc=`grep "$read_int" ${Directory path}/file1.txt| wc -l`
if [ $cnt_exc -gt 0 ]
then
int_1=0
else
int_2=0
fi
done < awk -F' ' '{ print $2 }' ${Directoty path}/test_file.txt
test_file.txt is the input file and file1.txt is a lookup file. But the above way is not working and giving me syntax errors near awk -F
I tried writing the output to a file. The following worked in command line:
more test_file.txt | awk -F' ' '{ print $2 }' > output.txt
This is working and writing the records to output.txt in command line. But the same command does not work in the unix script (It is a .scr file)
Please let me know where I am going wrong and how I can resolve this.
Thanks,
Visakh
The job of replacing multiple delimiters with just one is left to tr:
cat <file_name> | tr -s ' ' | cut -d ' ' -f 2
tr translates or deletes characters, and is perfectly suited to prepare your data for cut to work properly.
The manual states:
-s, --squeeze-repeats
replace each sequence of a repeated character that is
listed in the last specified SET, with a single occurrence
of that character
It depends on the version or implementation of cut on your machine. Some versions support an option, usually -i, that means 'ignore blank fields' or, equivalently, allow multiple separators between fields. If that's supported, use:
cut -i -d' ' -f 2 data.file
If not (and it is not universal — and maybe not even widespread, since neither GNU nor MacOS X have the option), then using awk is better and more portable.
You need to pipe the output of awk into your loop, though:
awk -F' ' '{print $2}' ${Directory_path}/test_file.txt |
while read readline
do
read_int=`echo "$readline"`
cnt_exc=`grep "$read_int" ${Directory_path}/file1.txt| wc -l`
if [ $cnt_exc -gt 0 ]
then int_1=0
else int_2=0
fi
done
The only residual issue is whether the while loop is in a sub-shell and and therefore not modifying your main shell scripts variables, just its own copy of those variables.
With bash, you can use process substitution:
while read readline
do
read_int=`echo "$readline"`
cnt_exc=`grep "$read_int" ${Directory_path}/file1.txt| wc -l`
if [ $cnt_exc -gt 0 ]
then int_1=0
else int_2=0
fi
done < <(awk -F' ' '{print $2}' ${Directory_path}/test_file.txt)
This leaves the while loop in the current shell, but arranges for the output of the command to appear as if from a file.
The blank in ${Directory path} is not normally legal — unless it is another Bash feature I've missed out on; you also had a typo (Directoty) in one place.
Other ways of doing the same thing aside, the error in your program is this: You cannot redirect from (<) the output of another program. Turn your script around and use a pipe like this:
awk -F' ' '{ print $2 }' ${Directory path}/test_file.txt | while read readline
etc.
Besides, the use of "readline" as a variable name may or may not get you into problems.
In this particular case, you can use the following line
sed 's/ /\t/g' <file_name> | cut -f 2
to get your second columns.
In bash you can start from something like this:
for n in `${Directoty path}/test_file.txt | cut -d " " -f 4`
{
grep -c $n ${Directory path}/file*.txt
}
This should have been a comment, but since I cannot comment yet, I am adding this here.
This is from an excellent answer here: https://stackoverflow.com/a/4483833/3138875
tr -s ' ' <text.txt | cut -d ' ' -f4
tr -s '<character>' squeezes multiple repeated instances of <character> into one.
It's not working in the script because of the typo in "Directo*t*y path" (last line of your script).
Cut isn't flexible enough. I usually use Perl for that:
cat file.txt | perl -F' ' -e 'print $F[1]."\n"'
Instead of a triple space after -F you can put any Perl regular expression. You access fields as $F[n], where n is the field number (counting starts at zero). This way there is no need to sed or tr.