Questions tagged [cat]

cat is a standard Unix utility used for concatenating files or printing specific file on the standard output.

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Shell scripting: Receiving error `cat: illegal option -- A` when passing `CA` as parameter to shell function, other 2 letter params work as expected

I thought this was a weird one-off glitch at first, but now I've found a second completely different bash function with the same behavior, so I'm reaching out for help because it's driving me mad. ...
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What is the difference between `cat EOF` and `cat EOT` and when should I use it?

I'm used to use cat > /path/to/file << EOF when I, in a bash script, printed more than one line into a file... I was checking old code of my company and I found the cat EOT instruction ...
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feed output of command to another command as file

I can make config file of tor with cat <<EOF command as follows : cat <<EOF SocksPort 9050 ControlPort 9150 DataDirectory /usr/var/lib/tor/torrc EOF but it can save output with redirect &...
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concatenate all the text files in all the sub folders into one giant text file

Ok so the situation is that I have an unknown number of sub-directories that all follow the same naming profile folder0, folder1, folder2, folder3 etc Now each folder will have 3 text files and these ...
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28 votes
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When using cat to create file, I have to type ctrl+d twice to finish the input, is this expected? [duplicate]

I just learned a trick to create a new file with the cat command. By my testing, if the last line is not followed by a newline, I have to type ctrl+d twice to finish the input, as demonstrated below. ...
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How to concatenate files in reverse order

I am looking to concatenate a list of files in a directory in the reverse order that they appear in the list. This is different from tac as tac will concatenate the files with reversed line order. ...
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What are the weird characters from an image file?

So i am pretty new to linux and i am learning basic commands. I am also very interested to know how things work under the hood, so sometime after i learned both the cat and nano commands, i tried ...
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"> $logfile" does not truncate, file size goes to 0 and a second later, is back to full size [duplicate]

I have a script that writes to a logfile like this: $ nohup myscript.sh > myscript.out 2>&1 & when the log file gets very large, I need to truncate it like this: > myscript.out I ...
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Why does cat command only read from stdin?

I'm trying to figure out why my cat command refuses to acknowledge the file I provide. I know that cat ignores filenames when they are absent or a - is provided, but I am not doing either of those ...
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How can `cat` read a file without a file descriptor?

I'm learning Linux procfs, which utilizes a virtual file system where operations like open, read, write, and release are processed by functions registered to it. I've left the open and release to null ...
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Sum of Column with Rows Specific and write that value to .txt file

I have number of text files which has 70000 rows and 2 column. I would like to sum entries of 2nd column from 40000 to 70000 row and value of sum is to written to new text file. e.g:-Suppose Data1_old....
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What are the benefits of this command line (/usr/bin/awk '{$1=$1};1') instead of pure cat

I am reading the AWS eic_harvest_hostkeys script and I don't understand this line: key=$(/usr/bin/awk '{$1=$1};1' < "${file}") What is the of benefit awk? Isn't key=$(/bin/cat "${...
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Running script in parallel using xargs and cat

I'm inserting a lot of CSV files into database. I want to do it in parallel, for example run 4 processes. Right now I do it with the script like this: find . -name "*.csv" | xargs -n 1 -P 4 ....
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How can I use nmap -p and cat 'file'?

I am trying to create a simple bash script that can run the "specific" port scan on mulitple IPs and Ports using nmap -p. The issue I am having is that when it reads the port# followed by ...
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Bash: Append rows from multiple files to one output file and add file name as column

This is a continuation of my previous question Bash: Choose row with the highest value in specified column in multiple files and create one output file with rows containing the max The solution I used ...
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Changing the place operator in a csv file

I've been editing a CSV file so I can import it into postgres. At this point I want to change the operator from column 5 to the left side of the column when the value is negative"-". When it ...
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Keep every process in 1 execution block in CSV handling

I asked some questions about how to handle a csv file and this result was numerous processes. Every month I get several TXT files in a Google Drive directory. I need to process, unite and load this ...
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Concat files with similar name in multiple subdirectories to new file

I am trying to concat all files with similar names but in different subdirectories. I found this solution for exact file matches but I am not sure how to adapt it for partial matches Create new ...
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3 votes
1 answer
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Linux find command to get all text in the file and print file path

I need get all the texts in the matching file in the folder , however at the same time need to get the matching file path as well . Can you please advise , how can I get the matching file path as well ...
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How to pipe an input into the cat command

I was reading an answer regarding sending large files from one Linux system to another by quick methods, and I was trying this solution The answer is saying that if you don't want to use the tar ...
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2 votes
2 answers
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Cat alternatives for writing terminal input to file?

When I want to quickly write something to a file that either get's pasted or manually input from the terminal, a quick cat > something.txt and Ctrl+D to close, is a nice shortcut. However of course ...
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When storing text on a USB drive, how do I make cat not hang?

Warning: I used these commands on a drive that had nothing on it (/dev/sdb). Do not attempt this on a drive with anything important on it. I was experimenting some, and I discovered that the ...
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Why Command "cata/etc/..." does not give me any results? [closed]

Why if I type: cat/etc/passwd or cat/etc/shadow the termnal give back me the message: no such file or directory found ? At least I should visualize me like user
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Why does `cat` followed by appending to a file seem to overwrite itself?

Consider the following two (sets of) commands: $ cat *.d | wc -l and $ rm -f tmp $ cat *.d >> tmp $ cat tmp | wc -l I would expect the two of these to output the same value. However, when I ...
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Load/Connect automatically to the Linux server session using Mputty

Looking for a help on Loading the putty sessions through Mputty. I can login to my app servers(Linux) only through Jumphost. After login to jumphost i need to perform the ssh to connect my App servers....
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I don't understand `cat` behaviour when running `cat | ls`

I know this is a useless command but I would like to understand why, wether in bash or zsh, when I enter cat | ls, cat will prompt me for input but only but will return after just one line whereas for ...
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Schrodinger's cat

When I run a cat command as a background process, $ cat & and then try to kill it, $ killall -v cat it says that it killed cat with signal 15, but also that cat was only stopped. Upon running $ ...
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1 vote
3 answers
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Merging files from most recent

I wish to get the command for merging files from the most recent to the oldest in bash from a particular directory. Meaning files with newer dates are saved before ones with older dates
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1 vote
1 answer
56 views

Fusing files line by line in a directory according to their type

I have a function, save, that is been called by other functions in a for loop and the function in question is to fuse files of the same type in a particular directory (copy the contents of each of the ...
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2 votes
3 answers
54 views

Return string of a line in a file with multiple line after a matching pattern

I have a file with multiple lines in it. I am trying to get a string that appears after a specific pattern... Here is the command i am trying to do: sed -n -e 's/^.*DB_PASS=//p' <<< $(cat /...
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4 votes
2 answers
807 views

How to visualize EOF in bash

/dev/null is a special Linux file which discards everything is written to itself and which provides EOF when read. I would like to read /dev/null to obtain and visualize this EOF. If I try: $ cat /dev/...
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2 votes
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ddrescue generate mapfile on partial image after cat --generate-mode

Having a HDD of 1TB (931.5G). I did: sudo sh -c 'cat /dev/sdf >disk_1t.img' But it stopped with read error at 908G. Thought next step, (should have been first), is to use gnu ddrescue. Problem is ...
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5 answers
239 views

Concatenate several files in directory with a prepend and append file

I have a directory of files that need two files merged to each one. For simplicity, let's use intro.txt and outro.txt. So, for files file1.txt to file3.txt I would like new files that contain intro....
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Why I must type something after cat << to make it work? [duplicate]

I've seen questions about cat << EOF so it's not duplicate. If I do: piotr@thinkpad:~$ cat << bash: syntax error near unexpected token `newline' I have error but when I do: piotr@thinkpad:...
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Can dd (or something like it) create an ISO encapsulating an Ubuntu virtual machine?

In a Lubuntu ISO booted in a VMware Player VM in lieu of that VM's Ubuntu installation, I can run this command to create an image of the Ubuntu installation: sudo dd if=/dev/sda bs=16M conv=sync,...
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1 answer
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cat ./* >> large.txt decreases in size

I'm a novice in bash scripting. I wrote a script that concatenates many files from different directories into large files #!/bin/bash for f in foo/$1/*; do if [ -d "$f" ]; then ...
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2 votes
1 answer
192 views

Playing, recording, and streaming sound with cat and /dev/dsp

A couple of comments on Hacker News suggest that, on FreeBSD, you can: use cat to send a file ( a .wav file for instance ) to the audio speaker (/dev/dsp). record from the mic using a similar method. ...
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2 answers
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what is difference between less and cat with respect to reading binary files?

While I'm trying to read the file /var/log/boot.log with less, I will get the this message: [amirreza@localhost ~]$ sudo less /var/log/boot.log "/var/log/boot.log" may be a binary file. See ...
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5 votes
2 answers
199 views

Evaluate large file with ^H and ^M characters

I have a logfile that contains many ^H and ^M characters, as the process that produces this file updates a text based progress bar. When using cat the output is evaluated and appears human readable ...
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1 vote
1 answer
499 views

Disable wake on usb after hibernation

Problem: I hibernate the computer at night and my cat wakes it by stepping on the keyboard. Yes, hibernate a.k.a. suspend to disk, with systemctl hibernate. Not suspend to ram. I used to think that, ...
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-1 votes
2 answers
137 views

Find directories and merge files

So I have a file system of thousands of subdirectories in the form 304880.US 906T89.DE 032848.UK 023455.UKREGRESS : Sometimes inside the folders there are other folders called 1, 2 and 3. Each end-...
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1 vote
1 answer
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How can I email a terminal session typescript without raw data?

I have a bash script that tries to kill two birds with one stone by running commands with script -c and writing the output to a log file so that I can monitor the progress, then email myself the ...
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Use output of cat with split command and specified output directory

I'm trying to split a long csv into files of 500 lines each. I want the output files in a specific directory, and I want to leave off the first line of the csv. I can use split and leave off the ...
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Concatenation script is not working as expected [duplicate]

I have the following script that is concatenating files in a directory in a particular fashion. I did some testing on a toy example and it is not doing what I thought it was doing. First, to describe ...
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2 votes
1 answer
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How to properly use tail to concatenate all hidden files [duplicate]

Issue I want to be able to : concatenate all files in a directory (regular and hidden), but I would also like to display the title of each file at the beginning of each concatenation. I found some ...
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5 votes
3 answers
870 views

Pipe globs to ls

Contents of file filelist: /some/path/*.txt /other/path/*.dat /third/path/example.doc I want to list those files, so I do: cat filelist | xargs ls But instead of expanding those globs, I get: ls: ...
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1 vote
1 answer
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cat command overwritten

By error I have execute "sudo nano cat filepathxxxx" and somehow I change the content. The cat command is no longer working and I can't install it I tried to execute "yum install ...
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3 votes
1 answer
219 views

Bash script : Cat multiple lines in file containing “$” characters [duplicate]

I'm doing a script to auto-install some stuff including a nginx web server. I'm creating the nginx conf file like this : cat >/etc/nginx/sites-available/bookstack.conf <<EOL server { listen ...
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2 votes
1 answer
505 views

Why am I seeing % as the line end when running cat file cmd [duplicate]

This really confused me, when I do a cat cmd, I always see something like % at the end of a file, but if I open the file on editor or sublime, it is gone. So how to make sure my file is in a correct ...
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  • 337
0 votes
2 answers
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Listing PCI Devices By Reading From File (Instead of lspci Command)

I need to read PCI device information from files. But it gives unusable output when I use command like that: cat /proc/bus/pci/05/00.0 Output: �h�� How could I fix this? OS: Debian-like Linux x64, ...
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