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0
votes
2answers
48 views

why does it take so long to read the top few lines of my file?

I have a huge text file ~ 33Gb and due to its size, I wanted to just read the first few lines of the file to understand how the file is organized. I have tried head, but it took like forever to even ...
11
votes
3answers
537 views

How can I work with binary in bash, to copy bytes verbatim without any conversion?

I am ambitiously trying to translate a c++ code into bash for a myriad of reasons. This code reads and manipulates a file type specific to my sub-field that is written and structured completely in ...
1
vote
2answers
46 views

What's the POSIX way to read an exact number of bytes from a file?

Just hit this problem, and learned a lot from the chosen answer: Create random data with dd and get "partial read warning". Is the data after the warning now really random? Unfortunately ...
0
votes
1answer
31 views

How can I get my bash script to remove the first n and last n lines from a variable?

I'm making a script to preform "dig ns google.com" and cut off the all of the result except for the answers section. So far I have: #!/bin/bash echo -n "Please enter the domain: " read d echo "You ...
0
votes
4answers
48 views

How do I insert the first line of one file into the first line of another?

I've got a head command to get the first line of a file and a sed command to insert before the first line of a file. How do I combine these so I can insert the extracted first line of one file before ...
-1
votes
1answer
35 views

Searching for most recent file (Display Unique)

If i have a Folder structure with 10 Sub dirs Each sub folder has the possibility to hold a version of a file (Older or newer) "Poor folder structure." I was looking to use Find to locate all files ...
1
vote
0answers
52 views

how to copy a piece of a text file byte-by-byte to another text file? dd, head, or?

I need to grab the first lines of a long text file for some bugfixing on a smaller file (a Python script does not digest the large text file as intended). However, for the bugfixing to make any sense, ...
3
votes
3answers
363 views

does head input > output copy all invisible characters to the new file?

I need to grab the first lines of a long text file for some bugfixing on a smaller file (a Python script does not digest the large text file as intended). However, for the bugfixing to make any sense, ...
3
votes
1answer
29 views

Head Script output explanation

So this shell script: #!/bin/bash head >/dev/null; head; almost always gives the same output when called with sequential numbers (e.g. seq 10000 | ./sscript) OUPUT: //blank line 1861 1862 ...
5
votes
2answers
235 views

Command to remove the first N number of lines in input

Background I am running an SSH server and have this user that I want to delete. I cannot delete this user because he is currently running a few processes that I need to kill first. This is the ...
0
votes
1answer
32 views

Head and Tail of a directory, set by the user

I have this script that will show the user the head or tail of the files that are inside a set directory (currently that is set as '~/bin/new/*'). This script works but i would like to allow the user ...
3
votes
3answers
346 views

List the first 4 lines of all the files in a given directory

What command could I create that will list the first 4 lines of all the files in a given directory?
-5
votes
1answer
1k views

Head and tail command

How can i do this exercise in unix? Create the following command: lshead.bash – list the first few lines of every file in a directory specified by the argument. This command should also allow options ...
1
vote
1answer
71 views

tail: illegal option — -53\r error while using head and tail on same file in single script

I am using a=`head -1 Rt.in` to get first value from my file and I am saving it as a variable then I am using same variable to tail -$a to tail last lines from my input. But it is giving an ...
1
vote
2answers
455 views

How can I print the second to last line of many files into one file? [duplicate]

I have many CSV files in one directory which have various lengths. I'd like to put the second to last line of each file into one file. I tried something like tail -2 * | head -1 > file.txt, then ...
2
votes
2answers
52 views

why my first pipe operation didn't remove newline character?

My nextermCensus.lis contains newline character and I am only interested in the first line, I'd like to remove newline character. but it doesn't work. so I have to use second method to remove it. ...
4
votes
3answers
240 views

How can I change the first line of a big gzip file without decompressing all of it?

I currently have a compressed file, A.gz which contains lots of tabulated data, including a header in the first line. I want to create another file, B.gz, which has the same data as the previous file, ...
1
vote
4answers
178 views

“head” only printing one line?

I've got a CSV file that's generated by saving as CSV from Excel. If I do "head" (or indeed "grep" or anything else) it only prints the first line: head -n 10 messy.csv 10,15,11,21 But if I open ...
-1
votes
2answers
160 views

select portion of file by line interval [duplicate]

I want to practice using head, uniq and cut, for this data here. I know this thread but it focuses too much on cat and external programs. I would like a simpler answer. I want to take interval from ...
5
votes
3answers
630 views

Compare the heads of two files in bash

I can do diff filea fileb to see the difference between files. I can also do head -1 filea to see the first line of filea or fileb. How can I combine these commands to show the difference between the ...
4
votes
5answers
3k views

Using head and tail to grab different sets of lines and saving into same file

So this is for homework, but I will not be asking the specific homework question. I need to use head and tail to grab different sets of line from one file. So like lines 6-11 and lines 19-24 and ...
1
vote
1answer
98 views

Problem with grep on multiple files and not getting desired output

I am using the below command on a file to extract few lines based on chr# ( different chromosome numbers). This is just a single file am working on. i have 8 such files and for each file I have to do ...
4
votes
3answers
503 views

Copy a specific percentage of each file in a directory to a new file

For example, we have N files (file1, file2, file3 ...) We need first 20% of them, the result directory should be like (file1_20, file2_20, file3_20 ...). I was thinking use wc to get the lines of ...
5
votes
2answers
4k views

Negative arguments to head / tail

Variants of this question have certainly been asked several times in different places, but I am trying to remove the last M lines from a file without luck. The second most voted answer in this ...
0
votes
0answers
64 views

Why does GNU head/tail read the whole file? [duplicate]

I have a huge file and want to see its beginning and end. However, when I use head and tail, it apparently tries to read the whole file. Since the file is larger than a terabyte, this takes a very ...
1
vote
1answer
1k views

Split very big xml file into little pieces with specific line number count

This is how I did to extract the first 100000 lines from my big xml file (2gb): head source.xml -n 100000 > part.xml How can I keep splitting them to 100000 line (or specific file size chunks) ...
4
votes
3answers
506 views

Time required to do pipe output to head/tail [duplicate]

There are lots of txt files in a directory. If I do time wc -l *.txt | head it takes real 0m0.032s user 0m0.020s sys 0m0.008s If I do time wc -l *.txt | tail it takes real 0m0.156s ...
5
votes
4answers
2k views

Is there a difference between read, head -1, and sed 1q?

The following commands seem to be roughly equivalent: read varname varname=$(head -1) varname=$(sed 1q) One difference is that read is a shell builtin while head and sed aren't. Besides that, is ...
2
votes
4answers
678 views

Only cat from specific line X (with a pattern) to other specific line Y (with a pattern)

A little extended problem from "cat line x to line y on a huge file": I have a huge file (2-3 GB). I'd like to cat/print only from the line having "foo:" to the line having "goo:". Assume that "foo:" ...
1
vote
3answers
100 views

Pulling lines n to m from list of files found

Ultimately I need to grab lines 3-53 from ever csv in each subdirectory. I grabbed the lines like so (cat isn't necessarily required): cat /[path]/[file].csv | head -53 | tail -51 And the files ...
2
votes
1answer
369 views

Command to print few consecutive lines from middle of a file [duplicate]

For a file containing 20 lines, lines 6-10 can be printed using following command: head -10 filename | tail -5 Can this exactly same thing be done without using 'head' and 'tail' commands ?? ...
1
vote
1answer
184 views

How to echo from specific line of a file to another specific line [duplicate]

Assume I have a file with about 10000 lines. How can I print 100 lines, starting from line 1200 to line 1300?
0
votes
1answer
406 views

How to make xargs ping and head output as expected?

Given an array of domains I would like to obtain their IP addresses, in the following format: 98.139.183.24 98.137.236.24 This script #!/bin/bash domains=(yahoo.com yahoo.ca) printf "%s\0" ...
2
votes
2answers
526 views

Use output from head to copy files with spaces

I have 11 files with spaces in its name in a folder and I want to copy the newest 10. I used ls -t | head -n 10 to get only the newest 10 files. When I want to use the expression in a cp statement I ...
6
votes
4answers
25k views

How to get lines 10 to 100 from a 200 line file into a new file [duplicate]

I have file with 200 lines. I need to extract lines from 10 to 100 and put them into a new file. How do you do this in unix/Linux? What are the possible commands you could use?
0
votes
1answer
417 views

removing the last line of a file not working? [duplicate]

I have this TXT file that is created by a bash script and at the end I want to remove the last line of that file that is an empty one. head --lines=-1 r3.txt > r4.txt sed '$d' r3.txt > r4.txt ...
1
vote
3answers
184 views

Is it possible to change the default COUNT value of tail and head?

The less command accepts its defaults with an environment variable LESS, so you can export LESS='-F -g -i -M -R -S -w -X -z-4' at the beginning of your session. Is it possible to change the ...
1
vote
2answers
865 views

will tail with piping read whole file?

I want to read a big log file with 10000 lines everytime. and I use this command: tail -c +offset somefile | head -n 10000 my question is, with the piping of head, will tail read the whole file? ...
4
votes
1answer
296 views

How can I colorize head, tail and less, same as I've done with cat?

I've got 'color cat' working nicely, thanks to others (see How can i colorize cat output including unknown filetypes in b&w?). In my .bashrc: cdc() { for fn in "$@"; do source-highlight ...
2
votes
1answer
4k views

Search and Filter Text on large log files

I use the tail, head and grep commands to search log files. Most of the time the combination of these 3 commands, in addition to using pipe, gets the job done. However, I have this one log that many ...
3
votes
1answer
329 views

POSIX head and tail not feature equivalent

The documentation for POSIX tail's -n option says that The origin for counting shall be 1; that is, -n +1 represents the first line of the file, -n -1 the last. So tail -n 10 (used later on the ...
12
votes
1answer
822 views

How to do `head` and `tail` on null-delimited input in bash?

find command can output names of files as a null-delimited strings (if -print0 is provided), and xargs can consume them with -0 option turned on. But in between, it's hard to manipulate that ...
1
vote
1answer
243 views

head command options and reading man files

I have two environments: Mac and Linux. I wonder about the head command: it can show just 2 lines of text if I invoke it like so: vim --version | head -2 I saw this online and ran to the man page ...
4
votes
0answers
82 views

Combing head and tail in a single call via pipe [duplicate]

On a regular basis, I am piping the output of some program to either head or tail. Now, suppose that I want to see the first AND last 10 lines of piped output, such that I could do something like ...
2
votes
1answer
151 views

Why can't I trim a file using `head`? [duplicate]

Given a file, foo.txt: 1 2 3 4 5 Say we want to change it to contain: 1 2 3 Why does head -n3 foo.txt > foo.txt leave foo.txt empty?
6
votes
2answers
3k views

Why does Subversion give a broken pipe error when piped into head?

If I do a svn log | head after the tenth line of output I get an error message: svn: Write error: Broken pipe What's going on here? I haven't seen any other command do this when used with head. ...
0
votes
1answer
170 views

Redirecting head output for update hosts file [duplicate]

Possible Duplicate: How can I make iconv replace the input file with the converted output? I'm writing a script to change the content of my hosts file but I got stuck on the head output ...
20
votes
9answers
40k views

Command to display first few and last few lines of a file

I have a file with many rows, and each row has a timestamp at the starting, like [Thread-3] (21/09/12 06:17:38:672) logged message from code..... So, I frequently check 2 things from this log file. ...
54
votes
6answers
93k views

cat line X to line Y on a huge file

Say I have a huge text file (>2GB) and I just want to cat the lines X to Y (e.g. 57890000 to 57890010). From what I understand I can do this by piping head into tail or viceversa, i.e. head -A ...
6
votes
1answer
972 views

Peculiar piping grep/head behavior

I'm helping the netadmin here with a perl regex to automate operating on some snapshots from our SAN and our scripts does stuff like this: varinit1=$(iscsiadm -m session | grep rbmsdata1 | head -n1 | ...