cat is a Unix utility used for concatenating files.

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flush output of cat

Now I'm using cat in a script to write into a file, but it seems the contents will be buffered. What can I do with it? cat >> comments.txt << EOF bla bla bla EOF
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attempting to put dynamic input data in a variable via cat method

I'm attempting to write a bash script that should be able to collect data from ttyS0 and put in a variable. I need to talk with a device on the serial line, that is a module able to receive AT ...
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1answer
42 views

Understanding of a Batch

I need your help to check if my understanding of those lines are correct. As a rookie in Unix, I work step by step. if [ $? -ne 0 ]; then I didn't find any correct explanations about the -ne but I ...
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Reuse output from command 1 in command 2 using a pipe

I've got a command in linux which returns a list of numbers. Now I need this numbers to form a directory path and cat the file located at that path. For example: myCommand returns: 1 10 30 40 And ...
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2answers
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Characters visible in vi, but not in cat.

I have a 300 lines file with ^@ character between each characters in the file. (I cannot post the entire contents for security reasons, so I am pasting only the first line) [mercury@app01 ftp_logs]$ ...
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1answer
37 views

How to assign the cat output of a bash script to a variable in another script

I have a bash script that produces a cat output when it takes an argument. I also have another bash script that executes the first bash script with an an argument that I want to produce cat outputs ...
3
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1answer
91 views

Mac OS X combine cp and cat to sequentially copy and rename files in list

I am using a MacBook Pro OS X 2013 model. I have a list of filenames in a text file named list.txt separated by line breaks list.txt exactly like this, but this list is going to be long e.jpeg ...
0
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1answer
44 views

How could I include a variable in a here document?

I am trying to use a user-defined global variable in a cat <<eof>> filename situation, but it's not working. I found what I want in simple cat << eof examples on this forum, which ...
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3answers
213 views

How to concatenate a variable number of csv, removing their header rows?

I have a directory with several hundred csv files whose filenames start with two digits {01..84}. Several hundred >> 84, so obviously some filenames start with the same prefix. I wish to concatenate ...
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2answers
53 views

Multiple arguments using xargs.

I know xargs can take many arguments like so. xargs -n5 -I{} echo {} but how do I put the arguments in a particular location I want do something like. xargs -n5 -I{} curl ...
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2answers
71 views

Stdin Input Behavior Between “cat” and “less”

When I issue cat, the terminal hangs waiting for stdin input. However, when less is issued, I get Missing filename ("less --help" for help). It is known that both less and cat accepts stdin input. ...
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788 views

Ctrl+D for ending terminal line input

If I do $cat > file.txt text<Ctrl+D><Ctrl+D> Question1: If I don't press enter, why do I have to press Ctrl+D twice? If I do $cat > file.txt pa bam pshhh<Ctrl+Z> [2]+ ...
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7answers
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How to kill a runaway cat?

Many times I accidentally run the cat command on files have contents up to few thousand lines. I try to kill the cat command with Ctrl+ C or Ctrl+Z, but both only take effect after the total output ...
0
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1answer
75 views

Command that prints file contents given filename on stdin

I have a command that produces some output part of which is actually a file name containing the full output data. I want to extract the file name (which I trivially do with cut) and then pass it to ...
0
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5answers
58 views

Is there a way to do a “full file buffering” inside a chain of piped commands?

Very often I do simple operations on a file, for example: cat file1.txt|sed -r 's/^ *//' to remove spaces at the beginning of the line. If I want to overwrite the file, the only way I know is: cat ...
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3answers
108 views

How to sort filenames with spaces in them and concatenate the files?

I have the misfortune of dealing with filenames that contain spaces. I want to concatenate files of which filenames contain spaces. I also want to sort the filenames numerically. Obviously the ...
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2answers
116 views

Less resource hungry alternative for piping `cat` into gzip for huge files

I have some files of which some are very large (like several GB), which I need to concatenate to one big file and then zip it, so something like this: cat file1 file2 file3 file4 | gzip > ...
3
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6answers
1k views

get first X characters from the cat command?

I have a text file I'm outputting to a variable in my shell script. I only need the first 50 characters however. I've tried using cat ${filename} cut -c1-50 but I'm getting far more than the first ...
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2answers
57 views

Cannot merge files using cat [duplicate]

I tried to open a lot of files (10,000+) with cat and them merging them into one like this: cat * > ~/Desktop/lol.xml But it returned this error: -bash: /bin/cat: Argument list too long This ...
2
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1answer
184 views

splitting a CSV and keeping the header without intermediate files [closed]

I am trying to split a dozen 100MB+ csv files into managable smaller files for a curl post. I have managed to do it but with a lot of temporary files and IO. It's taking an eternity. I am hoping ...
3
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1answer
300 views

grep not working in a for loop over a list

I have some log files. And I have a list of user ids. My log files are in a particular format log-yyyy-mm-dd e.g. log-2014-09-30 I am trying to search each userId in the log file. This is what I am ...
0
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1answer
129 views

reading file using for, while - behavior

Consider the below scenario 2 vms - 192.168.229.131, 192.168.229.132 Both the vms has it's ip as 192.168.229.151 & 192.168.229.152 in it's /etc/hosts file Say there are around 50 vms like i ...
3
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2answers
1k views

How to concatenate two files in a new one and sort the output in one line

I have two files with some names in them, when I ran cat file1 file2 | sort, the terminal shows the names sorted alphabetically, but when I run cat file1 file2 > file3 | sort I don't see the sorted ...
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2answers
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Joining files with cat confusion

If I do the following commands: $ cat picture.jpg > copy1.jpg and $ cat -v picture.jpg > copy2.jpg copy1.jpg is a perfect copy of picture.jpg, but copy2.jpg is a lot bigger than ...
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236 views

How to combine gunzipped fastq files?

How can I combine gzipped fastq files? I tried this for read 1 and read 2 zcat file_1.fastq.gz file_2.fastq.gz | gzip > combined.fastq.gz but it is giving me unequal number of reads. Why? Is ...
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208 views

Concatenate file contents AND names

I've been writing for many months. The files I create are dated files named like 2011-06-13.markdown with daily content. I've decided I want to have all the writing in one file instead but I'd like ...
2
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1answer
60 views

top not showing the memory usage of cat

I wanted to generate some waste file of 50 GB. so i wrote this eightnoteight@mr:~/ while true; do > cat txt >> tmp > cat tmp >> txt > done and when i ran top,watch to observe. ...
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2answers
42 views

Are `less textfile | col` and `cat textfile` the same?

Do less textfile | col and cat textfile accomplish the same thing? I wonder if man mysql | col -b > textfile and man mysql > textfile do the same?
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2answers
261 views

Why does cat x >> x loop?

The following bash commands go into an infinte loop: $ echo hi > x $ cat x >> x I can guess that cat continues to read from x after it has started writing to stdout. What is confusing, ...
5
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6answers
2k views

Command to output file content to stdout?

I know cat can do this, but its main purpose is to concatenate rather than just displaying the content. I also know about less and more, but I'm looking for something simple (not a pager) that just ...
1
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1answer
242 views

What does this `cat` statement do?

I'm new to Linux and trying to figure out what this statement in a Bash file does. I think it combines stdout, stderr and output it to the file $log is pointing to and append the multiline string to ...
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1answer
31 views

find file read it and search for specific identifier

I'm trying to find out in what files some specific identifiers are being used. I know the file's name and know the identifier, therefore I use the following command to achieve my desired result: find ...
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1answer
78 views

cat combining not all file formats - but which ones?

In GNU⁄Linux, combining files with cat works in miraculous ways – at least for me: cat part_* > /destination/file.xyz with the same file format for BOTH source and target file(s) ...
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Edit a command? [duplicate]

I'm using many basic commands of unix/linux. In Mac OS X Mavericks, I type cat for a file, but output was faulty. In example, content of the file named bar: foo bar Then: ...
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3answers
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cat /dev/null emptied my log file but size did not change

I'm quite new to Unix. Using Solaris 10 I faced the below issue. There is a large log file with size 9.5G. I tried to empty the file using the below command. # cat /dev/null file_log.txt By doing ...
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2answers
2k views

How to pipe a remote file to stdout over scp or sftp?

Using ssh, it is easy to print the contents of a file using ssh host 'cat file.txt' When ssh is disabled, and only SFTP is enabled, running the previous command gives the following error: ...
3
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1answer
76 views

Does cat never read from terminal?

Chapter 43. Redirecting Input and Output of Unix Power Tools, Third Edition has to say this about cat command: Standard input (stdin) normally comes from your keyboard. Many programs ignore ...
4
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2answers
152 views

(cp is to cat AS mv is to ?) mv multiple files into one file instead of cat * rm *

For everything in this question pretend the system only has one disk and filesystem. (we are not writing to different partitions, disks or filesystems) I am working on a project that cats very large ...
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2answers
65 views

Backed up over wrong hard drive

I've just written over the wrong hard drive using the command: sudo sh -c 'pv /dev/sdb >/dev/sdc' How do I go about undoing this? I was creating the first even backup of the drive, and I backed ...
0
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2answers
39 views

concatenate .out files

Can I combined multiple .out files with the cat command in bash or csh? Additionally I want only the header of first file to be concatenated and I was thinking of using the tail function for that. ...
3
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1answer
64 views

How to set default tabs only for cat?

I prefer to set tabs 4 however this may have some side effects, such as for example ls out put may look not properly aligned. How might I configure the terminal / cat to use four spaces for tabs for ...
4
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2answers
723 views

How to interleave the lines of two or more files?

I have tried to get the 2 files output in a single file. I have tried below command: cat file1 file2 but here file2 data is appending to file1. What I need is file1 1st line followed by file2 ...
14
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2answers
1k views

How do I “cat and follow” a file?

A file is being sequentially downloaded by wget. If I start unpacking it with cat myfile.tar.bz2 | tar -xj, it may unpack correctly or fail with "Unexpected EOF", depending on what is faster. How to ...
2
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2answers
2k views

continuous reading from named pipe (cat or tail -f)

I have configured rsyslog to log certain log events to /dev/xconsole: *.*;cron.!=info;mail.!=info |/dev/xconsole /dev/xconsole is a named pipe (fifo). If I want to see what is being logged, I ...
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2answers
2k views

Passing a variable to a bash script that uses 'EOF' and considers the variable a literal [closed]

in this script i end up with "$1" being saved to the /test file. #!/bin/bash cat > /test << 'EOF' $1 EOF the truth is.. i need to keep 'EOF' as 'EOF' because my argument($1) contains ...
2
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2answers
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“cat” command: how to automatically escape everything that might be a violation?

If you copy the contents of httpd.conf and then paste it into a cat command.. such as this one.. #!/bin/bash cat > /test << EOF pasted here.. EOF you run into this error: -bash: ...
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6answers
3k views

How to tell “cat” command to not hang on when there is no path provided?

I am simply trying to get a bash script to return the content of a text file. #!/bin/bash cat $1 the problem is.. when the path to a file is not fed to this bash script... how will it even close ...
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3answers
348 views

Replace $ with £ using cat Command

I have file test_output_archive.svd with some Dollar signs ($). I have generated a shell script Replace_dollar_pound.sh with cat command to replace dollar symbol with Pound (£) script is working on ...
0
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3answers
128 views

How to fork a “cat” command?

This is my bash script. #!/bin/bash oo="`cat /etc/httpd/conf/httpd.conf`"; cat > /a.txt << EOF $oo EOF it simply reads /etc/httpd/conf/httpd.conf and writes it to /a.txt, the problem has ...
15
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5answers
1k views

Is it possible to make zcat output text even if it's uncompressed? [duplicate]

The problem is I have some database dumps which are either compressed or in plain text. There is no difference in file extension etc. Using zcat on uncompressed files produces an error instead of the ...