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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126
votes
6answers
239k 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 /...
120
votes
8answers
31k views

dd vs cat — is dd still relevant these days?

I recently realized we can use cat as much as dd, and it's actually faster than dd I know that dd was useful in dealing with tapes where block size actually mattered in correctness, not just ...
8
votes
2answers
14k views

Why (and how) did using cat on binary files mess up the terminal?

If I understand the cat manual correctly: concatenate files and print on the standard output cat will take files as argument and print them on standard output. What I don't get is if I use the ...
25
votes
1answer
6k views

How to implement a horizontal cat? [duplicate]

Standard cat concatenates files line by line (row by row, if you will). I find myself needing a horizontal cat command more and more often recently; i.e. a command that takes a list of files and ...
50
votes
2answers
40k views

How do you use output redirection in combination with here-documents and cat?

Let's say I have a script that I want to pipe to another command or redirect to a file (piping to sh for the examples). Assume that I'm using bash. I could do it using echo: echo "touch somefile ...
49
votes
4answers
5k views

Should I care about unnecessary cats?

A lot of command-line utilities can take their input either from a pipe or as a filename argument. For long shell scripts, I find starting the chain off with a cat makes it more readable, especially ...
23
votes
9answers
53k 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. ...
12
votes
3answers
3k views

A virtual file containing the concatenation of other files

Is there a way of creating a filesystem object akin to this: mknod files p cat file1 file2 ... fileN > files but such that it can be seeked in, as if it were a regular file?
44
votes
6answers
186k views

How can I read line by line from a variable in bash?

I have a variable which contains multiline output of a command. What's the most effecient way to read the output line by line from the variable? For example: jobs="$(jobs)" if [ "$jobs" ]; then #...
9
votes
4answers
7k 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 ...
52
votes
5answers
156k views

With the Linux “cat” command, how do I show only certain lines by number

If I use cat -n text.txt to automatically number the lines, how do I then use the command to show only certain numbered lines.
70
votes
10answers
17k views

Is there a tool that combines zcat and cat transparently?

When handling log files, some end up as gzipped files thanks to logrotate and others not. So when you try something like this: $ zcat * you end up with a command line like zcat xyz.log xyz.log.1 xyz....
70
votes
5answers
13k views

Difference between “cat” and “cat <”

I was working through a tutorial and saw use of both cat myfile.txt and cat < myfile.txt. Is there a difference between these two sequences of commands? It seems both print the contents of a file ...
27
votes
12answers
43k views

How can I “cat” a file and remove commented lines?

I'd like to know if there is a way that I could cat file like php.ini and remove all lines starting with ; For example, if the file contained this: ; - Show all errors, except for notices ; ;...
16
votes
3answers
8k views

tee + cat: use an output several times and then concatenate results

If I call some command, for instance an echo I can use the results from that command in several other commands with tee. Example: echo "Hello world!" | tee >(command1) >(command2) >(command3)...
21
votes
2answers
24k views

Ctrl+D for ending terminal line input

If I do $ cat > file.txt textCtrl-DCtrl-D Question 1: If I don't press enter, why do I have to press Ctrl-D twice? If I do $ cat > file.txt pa bam pshhhCtrl-Z [2]+ Stopped ...
23
votes
5answers
18k views

Difference between cat and '>' to zero out a file

Are these two commands any different on how they go about zero-ing out files? Is the latter a shorter way of doing the former? What is happening behind the scenes? Both $ cat /dev/null > file....
5
votes
3answers
9k views

Concatenate specific files into one single file

In a folder containing X files, I need to concatenate Y files (where X > Y) together into a single text file. I have the filenames (of Y files) that I need to concatenate.
11
votes
2answers
27k views

How to highlight a word in the output of “cat”? [duplicate]

I can do the following to see if some word is available in the output of "cat": cat filename | grep word This filters the output and shows only those lines which contain "word". Now, is it possible ...
10
votes
2answers
7k views

Why does `cat`ing a file into itself erase it? [duplicate]

Possible Duplicate: IO redirection and the head command I just wanted to remove all but the first line of a file. I did this: head -1 foo.txt ... and verified that I saw only the first line. ...
25
votes
7answers
44k 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 ...
17
votes
5answers
12k views

How to make bash put prompt on a new line after cat command?

What I get: host:~ user$ cat example.txt some texthost:~ stas$ What I want to get: host:~ user$ cat example.txt some text host:~ stas$ Is there a way I can make cat behave like this? I'm using ...
15
votes
3answers
44k 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 ...
15
votes
3answers
42k views

How to read dash files

How can I read a dash file from the terminal other than delimiting it with ./ For example to read a - file we can read it by cat ./-file_name Q: Is there an alternative way to achieve the same ...
36
votes
7answers
4k views

Is it a UUOC (useless use of cat) to redirect one file to another?

If I want to make the contents of file2 match the contents of file1, I could obviously just run cp file1 file2. However, if I want to preserve everything about file2 except the contents—owner, ...
5
votes
4answers
754 views

saving output of another command

I need to select certain lines from the log file and also save them to a text file. I tried the following but none of them are working as expected. The file "todel.txt" shows 0 bytes. tail -f general....
24
votes
2answers
40k views

Fastest way to concatenate files

I've got 10k+ files totaling over 20GB that I need to concatenate into one file. Is there a faster way than cat input_file* >> out ? The preferred way would be a bash command, Python is ...
20
votes
2answers
10k views

Is it better to use cat, dd, pv or another procedure to copy a CD/DVD?

Background I'm copying some data CDs/DVDs to ISO files to use them later without the need of them in the drive. I'm looking on the Net for procedures and I found a lot: Use of cat to copy a medium: ...
17
votes
1answer
2k views

Make program first read from pipe, then from keyboard

Consider the interactive program interactive. I have to run this program fairly frequently, and each time I run it the first few commands are the same. Obviously, having to type those commands over ...
42
votes
4answers
12k views

How can I display syntax highlighting on a file?

Is there a variant of cat that outputs syntax-highlighted lines of code when used on a source file? An idea: maybe vi[m] or another editor can be asked to dump the syntax-highlighted contents of said ...
36
votes
6answers
132k 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 ...
28
votes
1answer
21k views

Append same text to many files using cat or echo?

How can I write the same content to many text files by using cat or echo in only one command? For example I want to write "hello" to file1 and file2. I tried: echo "hello" >> file1 file2 but ...
16
votes
3answers
14k views

Why does the less-than sign not work as a replacement for cat in bash?

I heard about "useless use of cat" and found some suggestions, but the following outputs nothing in my bash shell. < filename Using cat works as expected though. cat filename I'm using Fedora ...
7
votes
1answer
34k views

Read log file between two dates

I have to read log file between and my question is how to get only the text in the file wich is between two dates using unix commands? Every line contain date and I want to get the text in the file ...
22
votes
2answers
2k views

cat gives different error when opening non-existing file

Both of the following commands try to open a non-existing file foo, but the error messages are a little different. What could be the reason? $ cat foo cat: cannot open foo $ cat < foo -bash: foo: ...
8
votes
4answers
7k views

cat files in specific order based on number in filename

I have files named file.88_0.pdb, file.88_1.pdb, ..., file.88_100.pdb. I want to cat them so that file.88_1.pdb gets pasted after file.88_0.pdb, file.88_2.pdb after file.88_1.pdb, and so on. If I do ...
6
votes
4answers
4k views

cat special characters meaning

with cat, I use the -A flag and I can't find what these characters mean anywhere. For example: cat /proc/cpuinfo > output cat -A output One of the lines is this: processor^I: 7$ I know the $ ...
4
votes
1answer
1k views

How can i colorize cat output including unknown filetypes in b&w?

I like the colors I have in vim. Can I get my output similarly colorized when I do a cat? I like that I can use the colorize tool as in Colorized `cat` for source and script files?. I would like that ...
8
votes
2answers
2k views

What is produced after using cat on an image?

Let's say one creates a file like so: touch myFile You enter some text in it with vim or whatever, and then use cat myFile to spit the contents out into the terminal. Now, what happens when I use ...
5
votes
2answers
2k views

Encoding changed after running cat

After running cat on some files I get the infamous 'bushes': ␌⎺└⎻⎼␊⎽⎽␊␍ ├▒⎼ °␋┌␊. B␊├├␊⎼ ┤⎽␊ ├▒⎼'⎽ ≥ which I believe are result of encoding being changed. Is there any way to recover the terminal ...
5
votes
3answers
291 views

Why does cating an executable keep changing the title of PuTTY?

Its usually been seen that if an executable is cated, provided that its a huge file, it keeps on changing the title of the 'PuTTYapplication until its done printing the binary to the STDOUT with those ...
4
votes
2answers
6k views

What is the difference between > and >> (especially as it relates to use with the cat program)? [duplicate]

Suppose that I have a file called temp.txt. Using the cat program, I would like to add the contents of this file to the end of myfile.txt -- creating myfile.txt if it does not exist and appending to ...
3
votes
2answers
6k views

“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: command ...
-2
votes
3answers
2k 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 ...
11
votes
2answers
2k views

cat redirection

Say a file called abc exists in the current directory and it has some text in it. When you execute the command: cat abc > abc Why do the contents of the the file abc disappear? Why does the ...
10
votes
1answer
905 views

OS X, bash: less works on open file descriptors, cat doesn't

In a bash script I'm working on (which has to run on Ubuntu and OS X), I need to redirect the output of hundreds of commands to a file. Rather than appending &>... to all of them, I simply do ...
8
votes
6answers
3k views

Force newlines with cat wildcard printing

I want to use cat with wildcards in bash in order to print multiple small files (every file is one sentence) to standard output. However, the separate file contents are not separated by a newline, ...
3
votes
4answers
613 views

Concatenate table without header

I would like to concatenate several tables and just keeping the header in the first line (and thus not having a new header each time that a new table has been concatenate). Does anyone know how to do ...
2
votes
2answers
684 views

Sum of columns for rows containing a specific term

I'm wondering if there is any sed or awk command that can sum all columns for the rows with an identical identifier. For example, my file data.txt is set out as below, except that it contains ~1800 ...
2
votes
0answers
188 views

Data loss over ttyACM* when 'cat' command is used for data transfer

I have a development board which will have 3 ACM interfaces when connected to Ubuntu host and i want to transfer data from Host to Device over ttyACM3. I have followed the following procedure for ...