lsof stands for List Open Files.

1. Examples Of Data Collection Methods
2. Data Files

Examples of text files. A text document; A binary file is a file that contains information in the same format in which the information is held in memory i.e. In the binary form. In binary file, there is no delimiter for a line. Also no translations occur in binary files. As a result,binary files are faster and easier for a program to read and write than the text files. Sample CSV Data. In minutes, you can upload a data file and create and share interactive time- and map-based analyses and reports.

It is easy to remember lsof command if you think of it as “ls + of”, where ls stands for list, and of stands for open files.

It is a command line utility which is used to list the information about the files that are opened by various processes. In unix, everything is a file, ( pipes, sockets, directories, devices, etc.). So by using lsof, you can get the information about any opened files.

1. Introduction to lsof

Simply typing lsof will provide a list of all open files belonging to all active processes.

By default One file per line is displayed. Most of the columns are self explanatory. We will explain the details about couple of cryptic columns (FD and TYPE).

FD – Represents the file descriptor. Some of the values of FDs are,

• cwd – Current Working Directory
• txt – Text file
• mem – Memory mapped file
• mmap – Memory mapped device
• NUMBER – Represent the actual file descriptor. The character after the number i.e ‘1u’, represents the mode in which the file is opened. r for read, w for write, u for read and write.

TYPE – Specifies the type of the file. Some of the values of TYPEs are,

• REG – Regular File
• DIR – Directory
• FIFO – First In First Out
• CHR – Character special file

For a complete list of FD & TYPE, refer man lsof.

2. List processes which opened a specific file

You can list only the processes which opened a specific file, by providing the filename as arguments.

3. List opened files under a directory

You can list the processes which opened files under a specified directory using ‘+D’ option. +D will recurse the sub directories also. If you don’t want lsof to recurse, then use ‘+d’ option.

4. List opened files based on process names starting with

You can list the files opened by process names starting with a string, using ‘-c’ option. -c followed by the process name will list the files opened by the process starting with that processes name. You can give multiple -c switch on a single command line.

5. List processes using a mount point

Sometime when we try to umount a directory, the system will say “Device or Resource Busy” error. So we need to find out what are all the processes using the mount point and kill those processes to umount the directory. By using lsof we can find those processes.

The following will also work.

6. List files opened by a specific user

In order to find the list of files opened by a specific users, use ‘-u’ option.

Sometimes you may want to list files opened by all users, expect some 1 or 2. In that case you can use the ‘^’ to exclude only the particular user as follows

The above command listed all the files opened by all users, expect user ‘lakshmanan’.

7. List all open files by a specific process

You can list all the files opened by a specific process using ‘-p’ option. It will be helpful sometimes to get more information about a specific process.

8. Kill all process that belongs to a particular user

When you want to kill all the processes which has files opened by a specific user, you can use ‘-t’ option to list output only the process id of the process, and pass it to kill as follows

The above command will kill all process belonging to user ‘lakshmanan’, which has files opened.

Similarly you can also use ‘-t’ in many ways. For example, to list process id of a process which opened /var/log/syslog can be done by

Talking about kill, did you know that there are 4 Ways to Kill a Process?

9. Combine more list options using OR/AND

By default when you use more than one list option in lsof, they will be ORed. For example,

The above command uses two list options, ‘-u’ and ‘-c’. So the command will list process belongs to user ‘lakshmanan’ as well as process name starts with ‘init’.

But when you want to list a process belongs to user ‘lakshmanan’ and the process name starts with ‘init’, you can use ‘-a’ option.

The above command will not output anything, because there is no such process named ‘init’ belonging to user ‘lakshmanan’.

10. Execute lsof in repeat mode

lsof also support Repeat mode. It will first list files based on the given parameters, and delay for specified seconds and again list files based on the given parameters. It can be interrupted by a signal.

Repeat mode can be enabled by using ‘-r’ or ‘+r’. If ‘+r’ is used then, the repeat mode will end when no open files are found. ‘-r’ will continue to list,delay,list until a interrupt is given irrespective of files are opened or not.

Each cycle output will be separated by using ‘’. You also also specify the time delay as ‘-r’ ‘+r’.

In the above output, for the first 5 seconds, there is no output. After that a script named “inita.sh” is started, and it list the output.

Finding Network Connection

Network connections are also files. So we can find information about them by using lsof.

11. List all network connections

You can list all the network connections opened by using ‘-i’ option.

You can also use ‘-i4’ or ‘-i6’ to list only ‘IPV4’ or ‘IPV6‘ respectively.

12. List all network files in use by a specific process

You can list all the network files which is being used by a process as follows

You can also use the following

The above command will list the network files opened by the processes starting with ssh.

13. List processes which are listening on a particular port

You can list the processes which are listening on a particular port by using ‘-i’ with ‘:’ as follows

14. List all TCP or UDP connections

You can list all the TCP or UDP connections by specifying the protocol using ‘-i’.

15. List all Network File System ( NFS ) files

You can list all the NFS files by using ‘-N’ option. The following lsof command will list all NFS files used by user ‘lakshmanan’.

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A data file is a computer file which stores data to be used by a computer application or system, including input and output data. A data file usually does not contain instructions or code to be executed (that is, a computer program).

Most computer programs work with data files.

• 1Types of Data files

Types of Data files[edit]

Data files can be stored in two ways:

• Text files.
• Binary files.

Text files[edit]

A text file (also called ASCII files) stores information in ASCII characters. A text file contains human-readable characters. A user can read the contents of a text file or edit it using a text editor. In text files, each line of text is terminated, (delimited) with a special character known as EOL (End of Line) character. In text files some internal translations take place when this EOL character is read or written.^[1]

Examples of text files

• A text document

Binary files[edit]

A binary file is a file that contains information in the same format in which the information is held in memory i.e. in the binary form. In binary file, there is no delimiter for a line. Also no translations occur in binary files. As a result,binary files are faster and easier for a program to read and write than the text files. As long as the file doesn't need to be read or need to be ported to a different type of system, binary files are the best way to store program information.^[1]

Examples of binary files

• A JPEG image

Data file categories[edit]

Closed data file formats, frequently referred to as proprietary format files, have their metadatadata elements hidden, obscured or unavailable to users of the file. Application developers do this to discourage users from tampering with or corrupting the data files or importing the data into a competitor's application.

Open data format files have their internal structures available to users of the file through a process of metadata publishing. Metadata publishing implies that the structure and semantics of all the possible data elements within a file are available to users.

Examples of open data files include CSV, XLS and XML formats such as HTML for storing web pages or SVG for storing scalable graphics.^[2]

See also[edit]

Examples Of Data Collection Methods

References[edit]

1. ^ ^abMaking sense of file transfers: City edition. (1994, ). Boston Globe (Pre-1997 Fulltext)
2. ^Research Data Management Service Group. (n.d.). File Formats. Cornell University. Retrieved from https://data.research.cornell.edu/content/file-formats

Data Files