awk - pattern-directed scanning and processing language

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51
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6answers
11k views

Is there a basic tutorial for grep, awk and sed?

I've been a Linux user for a while, and I've a pretty decent understanding of most the common command line utilities. However, ones that come up and up again in relation to programming are grep, awk, ...
20
votes
8answers
26k views

Is there a way to get the min, max, median, and average of a list of numbers in a single command?

I have a list of numbers in a file, one per line. How can I get the minimum, maximum, median and average values? I want to use the results in a bash script. Although my immediate situation is for ...
20
votes
10answers
4k views

How can I write to the second line of a file from the command line?

I have an external program that produces an output file (largish, 20K lines possible). I need to insert a new line between the existing line 1 and line 2. I've been looking at awk and sed - I use ...
19
votes
11answers
2k views

Remove duplicate $PATH entries with awk command

I am trying to write a bash shell function that will allow me to remove duplicate copies of directories from my path environment. I was told that it is possible to achieve this with a one line ...
16
votes
3answers
3k views

Piping from grep to awk not working

I am trying to grep the ongoing tail of file log and get the nth word from a line. Example file: $ cat > test.txt <<EOL Beam goes blah John goes hey Beam goes what? John goes forget it Beam ...
16
votes
9answers
8k views

Tool in UNIX to subtract dates

Is there any tool in Solaris UNIX (so no GNU tool available) to subtract dates? I know that in Linux we have gawk that can subtract one date from another. But in Solaris the maximum we have is nawk ...
14
votes
9answers
2k views

There must be a better way to replace single newlines only?

I am in the habit of writing one line per sentence because I typically compile things to LaTex, or am writing in some other format where line breaks get ignored. I use a blank line to indicate the ...
14
votes
4answers
16k views

How to manipulate a CSV file with sed or awk?

How can I do the following to a CSV file using sed or awk? Delete a column Duplicate a column Move a column I have a big table with over 200 rows, and I'm not that familiar with sed.
12
votes
11answers
8k views

Grep huge number of patterns from huge file

I have a file that's growing about 200,000 lines a day, and it is all formed with blocks of three lines as such: 1358726575123 # key Joseph Brunner # name carpenter # job ...
12
votes
8answers
802 views

How to perform a multi line grep

How would you perform a grep for text that appears on two lines? For example: pbsnodes is a command I use that returns the utilization of a linux cluster root$ pbsnodes node1 state = free ...
11
votes
1answer
2k views

Making a progressbar with “dialog” from rsync output

I'm looking for a way to filter/redirect rsync output in a manner where it can be fed to the "dialog --gauge" command, so I can get a nice looking progressbar during file sync. Currently I have only ...
10
votes
5answers
958 views

Using grep or awk

To capture a particular pattern, awk and grep can be used. Why should we use one over the other. How does this work in the background? Which is faster and why? E.g If I had a log file and I wanted ...
10
votes
6answers
4k views

How can you combine all lines that end with a backslash character?

Using a common command line tool like sed or awk, is it possible to join all lines that end with a given character, like a backslash? For example, given the file: foo bar \ bash \ baz dude \ happy ...
10
votes
7answers
4k views

How to print the longest line in a file?

I'm looking for the simplest method to print the longest line in a file. I did some googling and surprisingly couldn't seem to find an answer. I frequently print the length of the longest line in a ...
9
votes
8answers
800 views

How to remove multiple newlines at EOF?

I have files that end in one or more newlines and should end in only one newline. How can I do that with Bash/Unix/GNU tools? Example bad file: 1\n \n 2\n \n \n 3\n \n \n \n Example corrected ...
9
votes
3answers
2k views

How to sort the string which combined with string + numeric using bash script?

This is the data what I want to sort. But sort treats the numeric to string, the data it no sorted as I expected. /home/files/profile1 /home/files/profile10 /home/files/profile11 ...
9
votes
3answers
4k views

Delete the first n bytes of files

I've got an extreme problem, and all of the solutions I can imagine are complicated. According to my UNIX/Linux experience there must be an easy way. I want to delete the first 31 bytes of each file ...
9
votes
3answers
2k views

Process last line first using awk

I have a data file that I want to normalize using awk, based on the last datapoint. Therefor, I would like to access the last data point first, to normalize the data, then process normally. The ...
9
votes
2answers
607 views

Script to quickly test all keyboard keys

I need to check some notebooks for bad keyboard keys, and so I'd like to speed that up as much as possible. I found nothing for this specific task, so my idea is a script that reads the pressed keys ...
8
votes
6answers
229 views

Grab certain contents of a file

So I know tools exist for this problem because I've heard about them, but I don't know what they are. I want to do something like filter out all data but the usernames in /etc/passwd. For example, I ...
8
votes
4answers
8k views

Remove line containing certain string and the following line

I use this cat foo.txt | sed '/bar/d' to remove lines containing the string 'bar' in the file. I would like however to remove those lines and the line directly after it. Preferably in sed, awk or ...
8
votes
6answers
1k views

Delete lines beginning with #

How do I delete lines beginning with a #, given that there can be whitespace on the left and right of the #? # Master socket provides access to userdb information. It's typically
8
votes
5answers
6k views

Remove comma between the quotes only in a comma delimited file

I have a input file delimited with commas (,). There are some fields enclosed in double quotes that are having a comma in them. Here is the sample row 123,"ABC, DEV 23",345,534.202,NAME I need to ...
8
votes
3answers
3k views

When using awk /pattern/ { print “text”} /patern/ {print “”} is there an ELSE pattern?

Let's say I have text file like: R1 12 324 3453 36 457 4 7 8 R2 34 2342 2525 25 25 26 26 2 2 R3 23 2342 32 52 54 543 643 63 R4 25 234 2342 4 234242 I want to use awk to process these lines ...
8
votes
2answers
177 views

Are there 2 ways to set awk vars via command line?

I noticed an O'Reilly awk example (1997) which assigned an awk variable by setting it on the command line after the program-text. It does work, but I can't find this syntax in man / info awk. Have I ...
7
votes
7answers
744 views

Slick one-liner to convert a list like “1: 2, 3, 4, 5” to “1.2, 1.3, 1.4, 1.5”

Let's say I have a file that looks something like this: 23: a, b, c, d 24: b, d, f 25: c, g and I want to get output like this: 23.a 23.b 23.c 23.d 24.b 24.d 24.f 25.c 25.g Of course it's not ...
7
votes
7answers
318 views

Swapping an unlimited number of columns

I have a file with columns. See below for an example: a b c ... z 1 2 3 ... 26 I'd like to swap all columns where the 1st becomes the last, the second becomes the one before last...etc.. z y x ...
7
votes
10answers
890 views

What's a good way to filter a text file to remove empty lines?

I have a .csv file (on a mac) that has a bunch of empty lines, e.g.: "1", "2", "lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum ...
7
votes
6answers
2k views

Is there any alternative to grep's -A -B -C switches (to print few lines before and after )?

grep -A 2 -B 3 prints 2 lines after the grep string and prints 3 lines before. grep -C 3 prints 3 Lines before and 3 lines after Unfortunately, the grep I'm using does not support these ...
7
votes
5answers
315 views

How to extract logs between two time stamps

I want to extract all logs between two timestamps. Some lines may not have the timestamp, but I want those lines also. In short, I want every line that falls under two time stamps. My log structure ...
7
votes
4answers
306 views

How to subtract rows (lines) with AWK

I'm trying to figure out how I can use AWK to subtract lines. For example, imagine the input file is: 30 20 The output would be: 10 Now, as a test I am trying to calculate the "Used" memory ...
7
votes
2answers
2k views

A shell script for joining two files

I want to write a shell script that get two files A and B, and get a result like this: File A: user_a tel_a addr_a user_b tel_b addr_b File B: process_1 user_a process_2 user_a process_3 user_b ...
7
votes
4answers
156 views

BEGIN and END with the awk command

According to the awk manual, BEGIN and END are not used to match input, but rather to provide start-up and clean-up information to the awk script. Here is the example given: ls -l | \ awk 'BEGIN { ...
6
votes
5answers
221 views

Get filesystem name and usage with `df -h`

df -h | grep test | sed -e 's/*%.^ //g;s/.*[ ^I]//' Output: /test /test/drv0 /test/drv1 df -h | grep test | cut -d '%' -f1 | sed -e 's/*%.^ //g;s/.*[ ^I]//' Output: 10 20 15 I want to ...
6
votes
4answers
496 views

uniq a csv file ignoring a column, awk maybe?

Given this file (annotations are not part of file, but form part of explanation)... x,a,001,b,c,d,y x,a,002,b,c,e,yy x,bb,003,b,d,e,y x,c,004,b,d,e,y x,c,005,b,d,e,y # nb - dupe of row 4 ...
6
votes
2answers
349 views

Counting number of times each IP address appears in log file

I have a file in the format as follows: $ cat file.txt 27.33.65.2 27.33.65.2 58.161.137.7 121.50.198.5 184.173.187.1 184.173.187.1 184.173.187.1 What's the best way to parse the file file.txt into ...
6
votes
4answers
218 views

number parsing in awk

I have a text file with numbers in second column and the numbers have thousand-separator and decimal-separator: 2014-01 2,277.40 2014-02 2,282.20 2014-03 3,047.90 2014-04 4,127.60 ...
6
votes
2answers
2k views

How to use regex as field separator in awk?

I'm trying to use regex as a field seperator in awk. From my reading this seems possible but I can't get the syntax right. rpm -qa | awk '{ 'FS == [0-9]' ; print $1 }' awk: cmd. line:1: { FS awk: ...
6
votes
4answers
1k views

How to remove multiple blank lines from a file?

I have some text-files I use to take notes in - just plain text, usually just using cat >> file. Occasionally I use a blank line or two (just return - the new-line character) to specify a new ...
6
votes
2answers
2k views

sed one-liner to delete any line that does not contain lowercase letters

So, basically THIS LINE WOULD BE DELETED and (THIS LINE WOULD ALSO BE DELETED) but Indeed, THIS LINE WOULD NOT
6
votes
3answers
21k views

How to use regex with AWK for string replacement?

Suppose there is some text from a file: (bookmarks ("Chapter 1 Introduction 1" "#1" ("1.1 Problem Statement and Basic Definitions 23" "#2") ("Exercises 31" "#30") ("Notes and References 42" "#34")) ) ...
6
votes
5answers
4k views

How to print certain columns by name?

I have the following file: id name age 1 ed 50 2 joe 70 I want to print just the id and age columns. Right now I just use awk: cat file.tsv | awk '{ print $1, $3 }' However, this ...
6
votes
3answers
2k views

AWK: wrap lines to 72 characters

$ awk 'length > 72' {HOW TO PRINT THE LINEs IN PCS?} msg ie I want it to add \n after 72 chars and continue, so initially you may need to remove all single \ns and the add them. It may be easier ...
6
votes
4answers
727 views

Find images by size: find / file / awk

I've been trying to find png image files a certain height (over 500px). I know that file will return image dimensions. Example: $ file TestImg1a.png TestImg1a.png: PNG image data, 764 x 200, ...
6
votes
1answer
159 views

How can I replace a string in a file(s)?

Replacing strings in files based on certain search criteria is a very common task. How can I replace string foo with bar in all files in the current directory? do the same recursively for sub ...
6
votes
5answers
3k views

Show sum of file sizes in directory listing

The Windows dir directory listing command has a line at the end showing the total amount of space taken up by the files listed. For example, dir *.exe shows all the .exe files in the current ...
6
votes
3answers
2k views

Why does awk do full buffering when reading from a pipe

I'm reading from a serial port connected to a gps device sending nmea strings. A simplified invocation to illustrate my point: $ awk '{ print $0 }' /dev/ttyPSC9 ...
6
votes
1answer
475 views

Why are capital letters included in a range of lower-case letters in an awk regex?

$ echo ABC | awk '$0 ~ /^[a-b]/' ABC $ echo ABC | awk '$0 ~ /^[a-a]/' $ echo ABC | awk '$0 ~ /^a/' $ You see. /[a-b]/ captures A, but /[a-a]/ or /a/ doesn't. Why?
5
votes
4answers
798 views

How to append end of every line with the line itself

This is in file.txt: redcar bluecar greencar Im looking for ways to make it become: redcar redcar bluecar bluecar greencar greencar I've tried many ways using sed with no luck
5
votes
7answers
10k views

How to print only last column?

echo -e 'one two three\nfour five six\nseven eight nine' one two three four five six seven eight nine how can I do some "MAGIC" do get this output?: three six nine UPDATE: I don't need it in this ...