I am trying to read in a basic, space delimited file in bash and I want to perform operations on the variables.
What is the nomenclature for referencing certain "columns" in bash?
I am trying to explicitly use bash. If there is useful documentation that references specifically how to delimit files and perform basic operations- that would be very useful.
An example of the text document I have would be as follows:
123456789 LastName FirstName 1 2 3
123456789 LastName FirstName 1 2 3
123456789 LastName FirstName 1 2 3
123456789 LastName FirstName 1 2 3
123456789 LastName FirstName 1 2 3
I would like to sort it and perform operations on multiple columns.
I have done this using awk, but I would like to do this in bash.
My awk implementation:
awk '{average = ($2 + $3 + $4)/3} {print (average, "["$1"]", $2",", $3); average = 0}' $'readme.txt'
How might this be achieved?
You'll want sort and cut for sorting and splitting respectively.
cut --delimiter=' ' --fields=LIST where LIST is a comma separated list of column indexes returns the sections of each space-split line denoted by the indexes in LIST.
sort --field-separator=' ' --keys=POS sorts the lines of your file and outputs them to stdout. --field-separator=' ' causes the positions to be delimited by spaces.
POS is F[.C][OPTS], where F is the field number and C the character position in the field; both are origin 1. If neither -t nor -b is in effect, characters in a field are counted from the beginning of the preceding whitespace. OPTS is one or more single-letter ordering options, which override global ordering options for that key. If no key is given, use the entire line as the key.
You can use expr and bc for the math.
wc -l will give you the count of total lines.
If you have headers which need ignoring, use tail -n +2 to get the whole file starting on the second line.
Strap everything together with pipes and subshells. In general the sort of processing you want is why awk has a place.
Related
I have the following list of strings in shell script:
something-7-5-2020.dump
another-7-5-2020.dump
anoter2-6-5-2020.dump
another-4-5-2020.dump
another2-4-5-2020.dump
something-2-5-2020.dump
another-2-5-2020.dump
8-1-2021
26-1-2021
20-1-2021
19-1-2021
3-9-2020
29-9-2020
28-9-2020
24-9-2020
1-9-2020
6-8-2020
20-8-2020
18-8-2020
12-8-2020
10-8-2020
7-7-2020
5-7-2020
27-7-2020
7-6-2020
5-6-2020
23-6-2020
18-6-2020
28-5-2020
26-5-2020
9-12-2020
28-12-2020
15-12-2020
1-12-2020
27-11-2020
20-11-2020
19-11-2020
18-11-2020
1-11-2020
11-11-2020
31-10-2020
29-10-2020
27-10-2020
23-10-2020
21-10-2020
15-10-2020
23-09-2020
So my goal is to sort them by date, but it's in dd-mm-yyyy and d-m-yyyy format and sometimes there's a word before like word-dd-mm-yyyy. I would like to create a function to sort the values like any other language so it ignores the first word, casts the date to a common format and compares that format. In javascript it would be something like:
arrayOfStrings.sort((a, b) => functionToOrderStrings())
My code to obtain the array is the following:
dumps=$(gsutil ls gs://organization-dumps/ambient | sed "s:gs\://organization-dumps/ambient/::" | sed '/^$/d' | sed 's:/$::' | sort --reverse --key=3 --key=2 --key=1 --field-separator=-)
echo "$dumps"
I would like to say that I've already searched this in Stackoverflow and none of the answers did help me, because all of them are oriented to sort dates in correct format and that's not my case.
If you have the results in a pipeline, involving an array seems completely superfluous here.
You can apply a technique called a Schwartzian transform: add a prefix to each line with a normalized version the data so it can be easily sorted, then sort, then discard the prefix.
I'm guessing something like the following;
gsutil ls gs://organization-dumps/ambient |
awk '{ sub("gs:\/\/organization-dumps/ambient/", "");
if (! $0) next;
sub("/$", "");
d = $0;
sub(/^[^0-9][^-]*-/, "", d);
sub(/[^0-9]*$/, "", d);
split(d, w, "-");
printf "%04i-%02i-%02i\t%s\n", w[3], w[2], w[1], $0 }' |
sort -n | cut -f2-
In so many words, we are adding a tab-delimited field in front of every line, then sorting on that, then discarding the first field with cut -f2-. The field extraction contains some assumptions which seem to be valid for your test data, but may need additional tweaking if you have real data with corner cases like if the label before the date could sometimes contain a number with dashes around it, too.
If you want to capture the result in a variable, like in your original code, that's easy to do; but usually, you should just run everything in a pipeline.
Notice that I factored your multiple sed scripts into the Awk script, too, some of that with a fair amount of guessing as to what the input looks like and what the sed scripts were supposed to accomplish. (Perhaps also note that sed, like Awk, is a scripting language; to run several sed commands on the same input, just put them after each other in the same sed script.)
Preprocess input to be in the format you want it to be for sorting.
Sort
Remove artifacts from step 1
The following:
sed -E '
# extract the date and put it in first column separated by tab
# this could be better, its just an example
s/(.*-)?([0-9]?[0-9]-[0-9]?[0-9]-[0-9]{4})/\2\t&/;
# If day is a single digit, add a zero in front
s/^([0-9]-)/0\1/;
# If month is a single digit, add a zero in front
s/^([0-9][0-9]-)([0-9]-)/\10\2/
# year in front? no idea - shuffle the way you want
s/([0-9]{2})-([0-9]{2})-([0-9]{4})/\3-\2-\1/
' input.txt | sort | cut -f2-
outputs:
another-2-5-2020.dump
something-2-5-2020.dump
another-4-5-2020.dump
another2-4-5-2020.dump
anoter2-6-5-2020.dump
another-7-5-2020.dump
something-7-5-2020.dump
26-5-2020
28-5-2020
5-6-2020
7-6-2020
18-6-2020
23-6-2020
5-7-2020
7-7-2020
27-7-2020
6-8-2020
10-8-2020
12-8-2020
18-8-2020
20-8-2020
1-9-2020
3-9-2020
23-09-2020
24-9-2020
28-9-2020
29-9-2020
15-10-2020
21-10-2020
23-10-2020
27-10-2020
29-10-2020
31-10-2020
1-11-2020
11-11-2020
18-11-2020
19-11-2020
20-11-2020
27-11-2020
1-12-2020
9-12-2020
15-12-2020
28-12-2020
8-1-2021
19-1-2021
20-1-2021
26-1-2021
Using GNU awk:
gsutil ls gs://organization-dumps/ambient | awk '{ match($0,/[[:digit:]]{1,2}-[[:digit:]]{1,2}-[[:digit:]]{4}/);dayt=substr($0,RSTART,RLENGTH);split(dayt,map,"-");length(map[1])==1?map[1]="0"map[1]:map[1]=map[1];length(map[2])==1?map[2]="0"map[2]:map[2]=map[2];map1[mktime(map[3]" "map[2]" "map[1]" 00 00 00")]=$0 } END { PROCINFO["sorted_in"]="#ind_num_asc";for (i in map1) { print map1[i] } }'
Explanation:
gsutil ls gs://organization-dumps/ambient | awk '{
match($0,/[[:digit:]]{1,2}-[[:digit:]]{1,2}-[[:digit:]]{4}/); # Check that lines contain a date
dayt=substr($0,RSTART,RLENGTH); # Extract the date
split(dayt,map,"-"); # Split the date in the array map based on "-" as the delimiter
length(map[1])==1? map[1]="0"map[1]:map[1]=map[1];length(map[2])==1?map[2]="0"map[2]:map[2]=map[2]; # Pad the month and day with "0" if required
map1[mktime(map[3]" "map[2]" "map[1]" 00 00 00")]=$0 # Get the epoch format date based on the values in the map array and use this for the index of the array map1 with the line as the value
}
END {
PROCINFO["sorted_in"]="#ind_num_asc"; # Set the ordering of the array
for (i in map1) {
print map1[i] # Loop through map1 and print the values (lines)
}
}'
Using GNU awk, you can do this fairly easy:
awk 'BEGIN{PROCINFO["sorted_in"]="#ind_num_asc"; FS="."}
{n=split($1,t,"-"); a[t[n]*10000 + t[n-1]*100 + t[n-2]]=$0}
END {for(i in a) print a[i]}' file
Essentially, we are asking GNU awk to traverse an array by index in ascending numeric order. Per line read, we extract the date. The date is always located before the <dot>-character and thus always in field 1 if the dot is the field separator (FS="."). We split the first field by the hyphen and use the total number of fields to extract the date. We convert the date simplistically to some number (YYYY*10000+MM*100+DD; DD<100 && MM*100 < 10000) and ask awk to sort it by that number.
It is now possible to combine the full pipe-line in a single awk:
$ gsutil ls gs://organization-dumps/ambient \
| awk 'BEGIN{PROCINFO["sorted_in"]="#ind_num_asc"; FS="."}
{sub("gs://organization-dumps/ambient/",""); sub("/$","")}
(NF==0){next}
{n=split($1,t,"-"); a[t[n]*10000 + t[n-1]*100 + t[n-2]]=$0}
END {for(i in a) print a[i]}'
I have a file named list.txt containing a (supplier,product) pair and I must show the number of products from every supplier and their names using Linux terminal
Sample input:
stationery:paper
grocery:apples
grocery:pears
dairy:milk
stationery:pen
dairy:cheese
stationery:rubber
And the result should be something like:
stationery: 3
stationery: paper pen rubber
grocery: 2
grocery: apples pears
dairy: 2
dairy: milk cheese
Save the input to file, and remove the empty lines. Then use GNU datamash:
datamash -s -t ':' groupby 1 count 2 unique 2 < file
Output:
dairy:2:cheese,milk
grocery:2:apples,pears
stationery:3:paper,pen,rubber
The following pipeline shoud do the job
< your_input_file sort -t: -k1,1r | sort -t: -k1,1r | sed -E -n ':a;$p;N;s/([^:]*): *(.*)\n\1:/\1: \2 /;ta;P;D' | awk -F' ' '{ print $1, NF-1; print $0 }'
where
sort sorts the lines according to what's before the colon, in order to ease the successive processing
the cryptic sed joins the lines with common supplier
awk counts the items for supplier and prints everything appropriately.
Doing it with awk only, as suggested by KamilCuk in a comment, would be a much easier job; doing it with sed only would be (for me) a nightmare. Using both is maybe silly, but I enjoyed doing it.
If you need a detailed explanation, please comment, and I'll find time to provide one.
Here's the sed script written one command per line:
:a
$p
N
s/([^:]*): *(.*)\n\1:/\1: \2 /
ta
P
D
and here's how it works:
:a is just a label where we can jump back through a test or branch command;
$p is the print command applied only to the address $ (the last line); note that all other commands are applied to every line, since no address is specified;
N read one more line and appends it to the current pattern space, putting a \newline in between; this creates a multiline in the pattern space
s/([^:]*): *(.*)\n\1:/\1: \2 / captures what's before the first colon on the line, ([^:]*), as well as what follows it, (.*), getting rid of eccessive spaces, *;
ta tests if the previous s command was successful, and, if this is the case, transfers the control to the line labelled by a (i.e. go to step 1);
P prints the leading part of the multiline up to and including the embedded \newline;
D deletes the leading part of the multiline up to and including the embedded \newline.
This should be close to the only awk code I was referring to:
< os awk -F: '{ count[$1] += 1; items[$1] = items[$1] " " $2 } END { for (supp in items) print supp": " count[supp], "\n"supp":" items[supp]}'
The awk script is more readable if written on several lines:
awk -F: '{ # for each line
# we use the word before the : as the key of an associative array
count[$1] += 1 # increment the count for the given supplier
items[$1] = items[$1] " " $2 # concatenate the current item to the previous ones
}
END { # after processing the whole file
for (supp in items) # iterate on the suppliers and print the result
print supp": " count[supp], "\n"supp":" items[supp]
}
This should be a simple fix but I cannot wrap my head around it at the moment.
I have a comma-delimited file called my_course that contains a list of courses with some information about them.
I need to get user input about the last two fields and change them accordingly.
Each field is constructed like:
CourseNumber,CourseTitle,CreditHours,Status,Grade
Example file:
CSC3210,COMPUTER ORG & PROGRAMMING,3,0,N/A
CSC2010,INTRO TO COMPUTER SCIENCE,3,0,N/A
CSC1010,COMPUTERS & APPLICATIONS,3,0,N/A
I get the user input for 3 things: Course Number, Status (0 or 1), and Grade (A,B,C,N/A)
So far I have tried matching the line containing the course number and changing the last two fields. I haven't been about to figure out how to modify the last two fields using sed so I'm using this horrible jumble of awk and sed:
temporary=$(awk -v status=$status -v grade=$grade '
BEGIN { FS="," }; $(NF)=""; $(NF-1)="";
/'$cNum'/ {printf $0","status","grade;}' my_course)
sed -i "s/CSC$cNum.*/$temporary/g" my_course
The issue that I'm running into here is the number of fields in the course title can range from 1 to 4 so I can't just easily print the first n fields. I've tried removing the last two fields and appending the new values for status and grade but that isn't working for me.
Note: I have already done checks to ensure that the user inputs valid data.
Use a simple awk-script:
BEGIN {
FS=","
OFS=FS
}
$0 ~ course {
$(NF-1)=status
$NF=grade
} {print}
and on the cmd-line, set three parameters for the various parameters like course, status and grade.
in action:
$ cat input
CSC3210,COMPUTER ORG & PROGRAMMING,3,0,N/A
CSC2010,INTRO TO COMPUTER SCIENCE,3,0,N/A
CSC1010,COMPUTERS & APPLICATIONS,3,0,N/A
$ awk -vcourse="CSC3210" -vstatus="1" -vgrade="A" -f grades.awk input
CSC3210,COMPUTER ORG & PROGRAMMING,3,1,A
CSC2010,INTRO TO COMPUTER SCIENCE,3,0,N/A
CSC1010,COMPUTERS & APPLICATIONS,3,0,N/A
$ awk -vcourse="CSC1010" -vstatus="1" -vgrade="B" -f grades.awk input
CSC3210,COMPUTER ORG & PROGRAMMING,3,0,N/A
CSC2010,INTRO TO COMPUTER SCIENCE,3,0,N/A
CSC1010,COMPUTERS & APPLICATIONS,3,1,B
It doesn't matter how much commas you have in course name as long as you look only at last two commas:
sed -i "/CSC$cNum/ s/.,[^,]*$$/$status,$grade/"
The trick is to use $ in pattern to match the end of line. $$ because of double quotes.
And don't bother building the "temporary" line - apply substitution only to line that matches course number.
I need pass a series of couples values which are arguments for a c++ software. So I wrote this script:
while read randomNumbers; do
lambda = $randomNumbers | cut -f1 -d ' '
mi = $randomNumbers | cut -f2 -d ' '
./queueSim mm1-queue $lambda $mi
done < "randomNumbers"
where the first arg is the first value for each line in the file "randomNumbers" and the second one in the second value (of course). I got a segfault and a "command not found".
How can I assign to lambda and mi valus got from the line and pass this variable to c++ software?
There's no need for cut. Let read split the line for you:
while read lambda mi; do
./queueSim mm1-queue $lambda $mi
done < randomNumbers
Note that it is also commonly used in conjunction with IFS to split the input line on different fields. For example, to parse /etc/passwd ( a file with colon separated lines ), you will often see:
while IFS=: read username passwd uid gid info home shell; do ...
I would recommend assigning the values like this:
lambda=$(echo $randomNumbers | cut -f1 -d ' ')
mi=$(echo $randomNumbers | cut -f2 -d ' ')
the way you do it, you actually try to run a command that is named like whatever is the current content of $randomNumbers.
Edit:
Another thing: since your columns are delimited by a whitespace character, you could also just read the entire line into an array whose elements are separated by whitespaces as well. One way to achieve this is:
columns=( $(echo "$randomNumbers" | grep -o "[^ ]*") )
./queueSim mm1-queue ${columns[#]::2}
The first line matches all substrings that are not containing any spaces separately and puts them into the array columns. The second line does the same thing as the corresponding one in your implementation: inserting the first two columns as parameters. Since is done with slicing: you take the entire array ${columns[#]}, but select a certain subsequence of it by applying the boundary ::2 on the right, which returns in every element of columns beginning from the left (position 0), that is not on a position >=2.
A: XXX (Done after 2 rounds)
A: YYY (Done after 1 rounds)
A: ZZZZ (Done after 4 rounds)
A: XXX (Done after 2 rounds)
A: ZZZZ (Done after 1 rounds)
A: YYY (Done after 2 rounds)
A: YYY (Done after 1 rounds)
For the above file, I want to extract certain names e.g. XXX, YYY, ZZZZ as well as the number of rounds for each name.
In the last, the result I expect is something like:
XXX 2 2
YYY 1 2 1
ZZZZ 4 1
I feel that I should use sed or awk, but not sure how to use them. Does anyone have good solutions? Thanks a lot.
awk '{ names[$2] = names[$2] " " $5; } END { for (name in names) print name " " names[name] }' file
Explanation:
Each input line is passed to the command names[$2] = names[$2] " " $5, which creates an array called names whose indices are not numeric--they're the words that appear as the 2nd field in your input lines: XXX, YYY, and ZZZZ. Their values accumulate the corresponding numbers in the 5th field of each line.
When the input file is exhausted, the END iterates through the index names, printing each name followed by its string of accumulated numbers.
I like Perl data structures (hash of arrays) for something like this:
perl -lane '
push #{$packets{$F[1]}}, $F[4]
}
END {
foreach $name (keys %packets) {print join(" ", $name, #{$packets{$name}})
}
'
This might work for you:
cut -d' ' -f2,5 file |
sort -sk1,1 |
sed ':a;$!N;s/^\(\(\S\+\).*\)\n\2/\1/;ta;P;D'
XXX 2 2
YYY 1 2 1
ZZZZ 4 1
Explanation:
Extract fields 2 and 5 i.e. on the first line XXX 2 using cut -d' ' -f2,5 file
Sort by first field but preserve order sort -sk1,1
Sed joins lines where the first field is the same and appends the second field. sed ':a;$!N;s/^\(\(\S\+\).*\)\n\2/\1/;ta;P;D'
Ths sed command works as follows:
Create a label :a
Append a newline to the current line (pattern space PS) then the next line unless it is the last line. $!N
Using the substitution command match the first field of the current line with the first field of the previous line and then remove it along with the preceeding newline. s/^\(\(\S\+\).*\)\n\2/\1/
If the substitution was successful branch to the label. ta
If the substitution was unsuccessful print the PS upto the first newline. P
Delete the PS upto and including the first newline, then start a new cycle without refreshing the PS. D