Frequently Asked Questions About Linux / UNIX » BASH Shell

Linux / Unix: View Overlapping Man Page With Same Names

nixCraft — Thu, 16 May 2013 19:06:02 +0000

I am a new Unix / Linux user. I am using whatis command to find man pages. But, I noticed that some man pages have a common names. For example, when I run whatis printf:
Outputs:
printf (1) - format and print data printf (1p) - write formatted output printf (3) - formatted output conversion printf (3p) - print formatted output printf [builtins] (1) - bash built-in commands, see bash(1)
How do I access overlapping man pages and what is the meaning of (1), (1p), (3), and so on?

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scp: Do not Overwrite Existing File On Linux or Unix System

nixCraft — Fri, 10 May 2013 20:03:49 +0000

I am a new Linux user. I use scp to upload files to net-storage provided CDN company. I do not want to overwrite the existing files. How can I prevent overwriting of files when using scp command under Linux, Mac OS X or Unix like operating systems?

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Linux / Unix: Find All Hidden Dot Directories and Delete

nixCraft — Sun, 05 May 2013 18:27:16 +0000

I need to clean up my backups stored on the nas server. I need to free up the disk space. How do I find out all hidden dot directories such as /nas01/backups/home/user/.gnome/, /nas01/backups/home/user/.gnome/ and so on and delete then in a single pass using Linux or Unix command line option? Please note that I do not want to delete nested hidden directories such as /nas01/backups/home/user/data/.xml, /nas01/backups/home/user/foo/bar/.level/.levle2/ and so on.

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Linux / Unix: Dig Command Find Out TTL (Time to Live) Value For DNS Records

nixCraft — Sun, 05 May 2013 05:53:32 +0000

I would like to see the Time-to-live (TTL) value for a 'AAAA' and A record for domains. How do I see Time-to-live (TTL) for a DNS record under Unix or Linux operating systems using command line options?

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Linux / Unix: Shell Remove Empty Lines

nixCraft — Wed, 24 Apr 2013 20:46:54 +0000

I am a new Linux user. I have text files with lots of empty lines. How do I delete all empty lines under Linux or Unix operating systems?

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Bash: .* Considered Harmful To Match Dot Files. Why?

nixCraft — Wed, 24 Apr 2013 19:49:53 +0000

How do I match dot files under Unix / Linux using bash shell? Why .* considered as harmful when matching dot files under bash shell?

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HowTo: Unix rm All Files In a Directory

nixCraft — Wed, 24 Apr 2013 10:03:53 +0000

I am a new Unix user. How do I rm (remove) all files in a directory called personal-files under Unix like operating systems?

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Bash Function: Find Number Of Arguments Passed

nixCraft — Wed, 24 Apr 2013 10:02:59 +0000

How do I find out number of arguments passed to my bash function called foo() under Unix like operating systems?

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HowTo: Check If a Directory Exists In a Shell Script

nixCraft — Sun, 14 Apr 2013 19:17:49 +0000

How do I check if a directory exists in a shell script under Linux or Unix like operating systems?

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AWK: Remove All Blank Spaces From String / Field

nixCraft — Sun, 14 Apr 2013 18:14:54 +0000

I need to parse the following text file: # example.net config user = www30021 group = ftp30020 uid = 30021 gid = 30020 tmp_path = /netapp42/shared/www/images/host.example.com/tmp.bin tmp_perms = defaults,nodev,nosuid,noexec jail = on location = /jails/apache/h/host.example.com/ sftp = on ftps = off php-cgi = on perl-cgi = off I need to find out value for each field and remove any blank spaces / white spaces from the field. How do I solve this problem using awk under Linux or Unix like operating systems?

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Linux / Unix Shell Script: Get The Current Directory

nixCraft — Tue, 09 Apr 2013 10:36:04 +0000

I am working on a shell script. I need to find out the current working directory. How do I get the current working directory under Bash or Ksh shell running on Linux or Unix like operating systems?

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Linux: Sort du -h (human-readable) Output By Size

nixCraft — Tue, 19 Mar 2013 20:09:54 +0000

I have a large number of files stored in ~/Downloads/ directory. How do I sort and print sizes in human readable format using du -h command under Ubuntu Linux LTS version 12.04 or any other Linux distributions?

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Linux / Unix Bash Shell List All Builtin Commands

nixCraft — Tue, 19 Mar 2013 10:55:26 +0000

Builtin commands are contained within the bash shell itself. How do I list all bash builtin commands under Linux / Apple OS X / *BSD / Unix like operating systems without reading large bash man page?

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Linux: Start Command In Background

nixCraft — Tue, 19 Mar 2013 10:18:29 +0000

I am a new Linux command line user. How do I start or run command in the background so that I can access command prompt immediately?

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FreeBSD Laptop: Find Out Battery Life Status Command

nixCraft — Wed, 13 Mar 2013 15:50:18 +0000

I know how to find out battery life status using Linux operating system. How do I monitor battery status on a laptop running FreeBSD version 9.x?

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RHEL / CentOS: Install and Activate Bash Autocomplete Feature

nixCraft — Wed, 13 Mar 2013 10:49:10 +0000

How do I use bash auto complete features with various command on CentOS / RHEL / Fedora / Scientific Linux based systems?

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Linux / Unix: Read a Man Page From Local Directory

nixCraft — Sun, 10 Mar 2013 22:33:18 +0000

I have a man page stored in my home directory called ~/foo.1. How do I read a $HOME/foo.1 man page file? How can I read the file called ~/foo.1 as a manpage with man command?

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Linux / Unix Find Command: Avoid Permission Denied Messages

nixCraft — Sun, 10 Mar 2013 09:37:07 +0000

When I type find . -type d -name "foo" command I get Permission denied error messages. How do I exclude all "permission denied: messages from the find command under Linux or Unix like operating systems?

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Bash Shell: Remove (Trim) White Spaces From String / Variable

nixCraft — Tue, 15 Jan 2013 23:44:19 +0000

I have a bash variable as follows: output="$(awk -F',' '/Name/ {print $9}' input.file)" How do trim leading and trailing whitespace from bash variable called $output? How do I trim trailing whitespace from $output?

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Linux: Find Out What Process Are Using Swap Space

nixCraft — Tue, 15 Jan 2013 19:59:19 +0000

The top and free command display the total amount of free and used physical and swap memory in the server. How do I determine which process is using swap space under Linux operating systems? How do I find out swap space usage of particular process such as memcached?

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