Logical entities that contain data in a filesystem. Use this tag if your question: is about programs that create files (e.g. gzip, tar, zip); deals with characteristics of files (permissions, size, path/location); or is about management of files (renaming, listing, moving, removing). For operating ...

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268
votes
6answers
517k 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 ...
104
votes
3answers
104k views

How to tell gzip to keep original file?

I would like to compress a text file using gzip command line tool while keeping the original file. By default running the following command gzip file.txt results in modifying this file and renaming ...
86
votes
6answers
7k views

How are “/dev” Linux files created?

There are special files in Linux that are not really files... The most notable and clear examples of these are in the dev folder, "files" like: /dev/null - Ignores anything you write to the file /...
81
votes
17answers
25k views

Is there an easy way to replace duplicate files with hardlinks?

I'm looking for an easy way (a command or series of commands, probably involving find) to find duplicate files in two directories, and replace the files in one directory with hardlinks of the files in ...
80
votes
2answers
126k views

Empty the contents of a file

I am aware of three methods to delete all entries from a file. They are >filename touch filename filename < /dev/null Of these three I abuse >filename the most as that requires the ...
79
votes
10answers
118k views

How do I loop through only directories in bash?

I have a folder with some directories and some files (some are hidden, beginning with dot). for d in *; do echo $d done will loop through all files, but I want to loop only through directories. ...
76
votes
9answers
124k views

How can I get the size of a file in a bash script?

How can I get the size of a file in a bash script? How do I assign this to a bash variable so I can use it later?
75
votes
5answers
26k views

What's the point in adding a new line to the end of a file?

Some compilers (especially C or C++ ones) give you warnings about: No new line at end of file I thought this would be a C-programmers-only problem, but github displays a message in the commit view: ...
73
votes
10answers
58k views

How can I edit multiple files in VIM?

I know I can open multiple files with vim by doing something like vim 2011-12*.log, but how can I switch between files and close the files one at a time? Also, how can I tell the file name of the ...
71
votes
6answers
177k views

How can I count the number of lines of a file with common tools?

I am redirecting grep results to a file, and then using cat to show its contents on the screen. I want to know how many lines of results I have in my results file and then add it to some counter. ...
71
votes
1answer
7k views

Why does the following script delete itself?

If you create an executable file with the following contents, and run it, it will delete itself. How does this work? #!/bin/rm
70
votes
6answers
60k views

What is a Superblock, Inode, Dentry and a File?

From the article Anatomy of the Linux file system by M. Tim Jones, I read that Linux views all the file systems from the perspective of a common set of objects and these objects are superblock, inode, ...
69
votes
6answers
201k views

How to get over “device or resource busy”?

I tried to rm -rf a folder, and got "device or resource busy". In Windows, I would have used LockHunter to resolve this. What's the linux equivalent? (Please give as answer a simple "unlock this" ...
68
votes
6answers
58k views

How to remove duplicate lines inside a text file?

A huge (up to 2 GiB) text file of mine contains about 100 exact duplicates of every line in it (useless in my case, as the file is a CSV-like data table). What I need is to remove all the repetitions ...
67
votes
12answers
84k views

Efficiently delete large directory containing thousands of files

We have an issue with a folder becoming unwieldy with hundreds of thousands of tiny files. There are so many files that performing rm -rf returns an error and instead what we need to do is something ...
65
votes
3answers
220k views

Get file created/creation time? [duplicate]

Possible Duplicate: How do I do a ls and then sort the results by date created? Is there a command in Linux which displays when the file was created ? I see that ls -l gives the last modified ...
64
votes
3answers
256k views

Where are Apache file access logs stored?

Does anyone know where file access logs are stored, so I can run a tail -f command in order to see who is accessing a particular file. I have XAMPP, which is an Apache server installed on my machine, ...
63
votes
4answers
21k views

locate vs find: usage, pros and cons of each other

In Linux and Unix systems there are two common search commands: locate and find. What are the pros and cons of each? When one have benefits over the other?
58
votes
3answers
36k views

Why can rm remove read-only files?

If I create a file and then change its permissions to 444 (read-only), how come rm can remove it? If I do this: echo test > test.txt chmod 444 test.txt rm test.txt ...rm will ask if I want to ...
56
votes
5answers
32k views

Find duplicate files

Is it possible to find duplicate files on my disk which are bit to bit identical but have different file-names?
55
votes
7answers
122k views

How to find creation date of file?

I want to find out the creation date of particular file, not modification date or access date. I have tried with ls -ltrh and stat filename.
51
votes
8answers
127k views

How to list all files ordered by size

I would like to list all files in the order of big to small in size and the files could be present anywhere in a certain folder.
50
votes
3answers
70k views

How do I do a ls and then sort the results by date created?

In what order are the dated ordered by? Certainly not alphanumeric order. ls -lt sorts by modification time. But I need creation time.
49
votes
8answers
6k views

On Unix systems, why do we have to explicitly `open()` and `close()` files to be able to `read()` or `write()` them?

Why do open() and close() exist in the Unix filesystem design? Couldn't the OS just detect the first time read() or write() was called and do whatever open() would normally do?
48
votes
7answers
4k views

How are file types known if not from file suffix?

I would like to know how file types are known if filenames don't have suffixes. For example, a file named myfile could be binary or text to start with, how does the system know if the file is binary ...
47
votes
4answers
32k views

Clone ownership and permissions from another file?

Is there a command or flag to clone the user/group ownership and permissions on a file from another file? To make the perms and ownership exactly "like" that of another file?
45
votes
2answers
4k views

Why is rm allowed to delete a file under ownership of a different user?

From the post Why can rm remove read-only files? I understand that rm just needs write permission on directory to remove the file. But I find it hard to digest the behaviour where we can easily delete ...
44
votes
2answers
94k views

timestamp, modification time, and created time of a file

I just know that ls -t and ls -f give different sorting of files and subdirectories under a directory. What are the differences between timestamp, modification time, and created time of a file? How ...
44
votes
5answers
77k views

Script to monitor folder for new files?

How do I detect new files in a folder with a bash script? I would like to process the files as soon as they are created in the folder. Is this possible to do so or do I have to schedule a script with ...
44
votes
3answers
77k views

Find and remove large files that are open but have been deleted

How does one find large files that have been deleted but are still open in an application? How can one remove such a file, even though a process has it open? The situation is that we are running a ...
42
votes
3answers
89k views

How to merge all (text) files in a directory into one?

I've got 14 files all being parts of one text. I'd like to merge them into one. How to do that?
42
votes
8answers
62k views

How do I grep recursively through .gz files?

I am using a script to regularly download my gmail messages that compresses the raw .eml into .gz files. The script creates a folder for each day, and then compresses every message into its own file. ...
41
votes
4answers
52k views

last time file opened

Is it possible to get the time when file was opened last time and sort all files in a directory by those times?
41
votes
8answers
93k views

List only regular files (but not directories) in current directory

I can use ls -ld */ to list all the directory entries in the current directory. Is there a similarly easy way to just list all the regular files in the current directory? I know I can use find find . ...
40
votes
5answers
40k views

How to determine which process is creating a file? [duplicate]

Given file path, how can I determine which process creates it (and/or reads/writes to it)?
39
votes
7answers
50k views

Find the total size of certain files within a directory branch

Assume there's an image storage directory, say, ./photos/john_doe, within which there are multiple subdirectories, where many certain files reside (say, *.jpg). How can I calculate a summary size of ...
37
votes
4answers
49k views

What's the best way to join files again after splitting them?

If I have a large file and need to split it into 100 megabyte chunks I will do split -b 100m myImage.iso That usually give me something like xaa xab xac xad And to get them back together I have ...
35
votes
3answers
87k views

Sort based on the third column

I'm facing a huge 4-columns file. I'd like to display the sorted file in stdout based on its 3rd column: cat myFile | sort -u -k3 Is that enough to perform the trick?
34
votes
6answers
7k views

How does Linux choose which application to open a file?

If a file tells the OS its file format, how does the OS choose which application to open it by default? In Windows, is the association stored in the registry table? How does Linux choose which ...
33
votes
4answers
2k views

Does bash open files in O_APPEND when using “>>” on linux?

If we use echo 1234 >> some-file then Documentation says that the output is appended. My guess is that, if some-file does not exist, then O_CREAT will make a new file. If > was used, then ...
32
votes
7answers
3k 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, ...
32
votes
3answers
3k views

Can a bash script be hooked to a file?

I want a script to sleep unless a certain file is modifed/deleted (or a file created in a certain directory, or ...). Can this be achieved in some elegant way? The simplest thing that comes to my mind ...
32
votes
9answers
20k views

How to delete this undeletable directory?

I untarred a corrupt tar file, and managed to end up with some directory that I can not delete, If I try to delete it, it seems like it can not be found, but ls shows it's present, both with bash and ...
31
votes
3answers
17k views

Pseudo files for temporary data

I often want to feed relatively short string data (could be several lines though) to commandline programs which accept only input from files (e.g. wdiff) in a repeated fashion. Sure I can create one ...
31
votes
4answers
24k views

Reading lines from a file with bash: for vs. while

I'm trying to read a text file and do something with each line, using a bash script. So, I have a list that looks like this: server1 server2 server3 server4 I thought I could loop over this using ...
31
votes
7answers
3k views

How can I trick a process into thinking a file doesn't exist?

I have a program that stores its settings in ~/.config/myprogram that I use both interactively and with a batch queuing system. When running interactively, I want this program to use my configuration ...
31
votes
4answers
2k views

Append huge files to each other without copying them

There are 5 huge files ( file1, file2, .. file5) about 10G each and extremely low free space left on the disk and I need to concatenate all this files into one. There is no need to keep original files,...
31
votes
5answers
54k views

How can I increase the number of inodes in an ext4 filesystem?

I had a problem (new to me) last week. I have a ext4 (Fedora 15) filesystem. The application that runs on the server suddenly stopped. I couldn't find the problem at first look. df showed 50% ...
30
votes
2answers
22k views

What happens when you delete a hard link?

If you do rm myFile where myFile is a hard link, what happens?
30
votes
3answers
11k views

Flattening a nested directory

This is probably very simple, but I can't figure it out. I have a directory structure like this (dir2 is inside dir1): /dir1 /dir2 | --- file1 | --- file2 What is ...