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Commands by mpb

Commands by mpb from sorted by
Terminal - Commands by mpb - 23 results
export HISTIGNORE=' cd "`*: PROMPT_COMMAND=?*?'
2011-10-18 19:58:39
User: mpb
Functions: cd export
1
Up
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Define shell variable HISTIGNORE so that comments (lines starting with #) appear in shell history

I was surprised to find that with RedHat bash, I could not find any comment lines (begining with #) in my bash shell history. Surprised because in Mageia Linux this works. It turns out that RedHat's bash will keep comment lines if in my .bashrc, I define:

export HISTIGNORE=' cd "`*: PROMPT_COMMAND=?*?'

Why have comment lines in shell history? It's a handy and convenient way to make proto-commands (to be completed later) and for storing brief text data that is searchable in shell history.

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< /etc/passwd sed -n "/^bin:/,/^lp:/p"
2011-10-18 13:33:12
User: mpb
Functions: sed
0
Up
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display lines in /etc/passwd between line starting ...

[continued]...with "bin:" and line starting with "lp:".

This specific example with /etc/passwd shows the power of sed to extract data from text files.

Here we see an extract from /etc/passwd beginning with the line starting with "bin:" and ending with the line starting with "lp:".

Note also, placing the STDIN redirection at the start of the command makes it easy to recall and modify the command parameters line in shell history.

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urpmi.addmedia --update google-talkplugin http://dl.google.com/linux/talkplugin/rpm/stable/$(uname -m | sed -e "s/i.86/i386/")
2011-04-30 23:01:36
User: mpb
Functions: sed uname
-1
Up
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Define Google Talk plugin urpmi media source for Mandriva/Mageia (works for both 32-bit and 64-bit systems)

This command adds a urpmi media source called "google-talkplugin" to the urpmi configuration on Mandriva or Mageia. Needs to be run as root. We specify the option "--update" so that when Google provides a newer version of Google Talk plugin in their download system then running a system update (eg: "urpmi --auto-update") will result in our copy of Google Talk plugin getting updated (along with any other Mandriva/Mageia pending updates).

To install Google Talk plugin from this source, use:

urpmi google-talkplugin # install plugin used for voice and video Google chat via gmail

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urpmi.addmedia --update google-chrome http://dl.google.com/linux/chrome/rpm/stable/$(uname -m | sed -e "s/i.86/i386/")
2011-04-30 14:02:34
User: mpb
Functions: sed uname
-1
Up
Down
Define Google Chrome urpmi media source for Mandriva/Mageia (works for both 32-bit and 64-bit systems)

This command adds a urpmi media source called "google-chrome" to the urpmi configuration on Mandriva or Mageia. Needs to be run as root. We specify the option "--update" so that when Google provides a newer version of Google Chrome web browser in their download system then running a system update (eg: "urpmi --auto-update") will result in our copy of Google Chrome getting updated (along with any other Mandriva/Mageia pending updates).

To install Google Chrome from this source, use:

urpmi google-chrome-stable #install Google chrome web browser

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urpmi.removemedia -a && urpmi.addmedia --distrib --mirrorlist
2011-03-27 15:29:42
User: mpb
0
Up
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reset Mageia urpmi media sources to network only

On Mageia (and Mandriva) Linux, this command will clear your existing urpmi configuration and configure it to use only network sources. It can be useful after you have installed from CD/DVD and

don't want to continually be prompted to insert CD/DVD each time you install a package.

acknowledgement: blino

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rpm -q --whatprovides $filename
2011-02-09 23:28:15
User: mpb
Functions: rpm
0
Up
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find the rpm package name that provides a specific file

For Linux distributions using rpm (eg Mandriva), this command will find the rpm package name that provides a file.

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sort_csn () { echo "${1}" | sed -e "s/,/\n/g"| sort -nu | awk '{printf("%s,",$0)} END {printf("\n")}' | sed -e "s/,$//"; }
2011-01-26 15:18:08
User: mpb
Functions: awk echo sed sort
0
Up
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sort a list of comma separated numbers: sort_csn

"sort_csn" is a function to sort a comma separated list of numbers.

Define the the function with this:

sort_csn () { echo "${1}" | sed -e "s/,/\n/g"| sort -nu | awk '{printf("%s,",$0)} END {printf("\n")}' | sed -e "s/,$//"; }

Use the function like this:

sort_csn 443,22,80,8200,1533,21,1723,1352,25

21,22,25,80,443,1352,1533,1723,8200

One example where this is useful is when port scanning with nmap and getting a list of open ports in random order. If you use Nessus, you may need to create a scan policy for that set of specific ports and it is clearer to read with the port numbers in ascending order (left to right).

Caveat: no spaces in the comma separated list (just number1,number2,number3,etc).

A variation of this to sort a comma separated list of strings:

sort_css () { echo "${1}" | sed -e "s/,/\n/g"| sort -u | awk '{printf("%s,",$0)} END {printf("\n")}' | sed -e "s/,$//"; }

usage:

sort_css apples,pears,grapes,melons,oranges

apples,grapes,melons,oranges,pears

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# cd $partition; dd if=/dev/zero of=ShredUnusedBlocks bs=512M; shred -vzu ShredUnusedBlocks
2009-06-21 14:17:22
User: mpb
Functions: cd dd shred
8
Up
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securely erase unused blocks in a partition

This command securely erases all the unused blocks on a partition.

The unused blocks are the "free space" on the partition.

Some of these blocks will contain data from previously deleted files.

You might want to use this if you are given access to an old computer and you do not know its provenance.

The command could be used while booted from a LiveCD to clear freespace space on old HD.

On modern Linux LiveCDs, the "ntfs-3g" system provides ReadWrite access to NTFS partitions thus enabling this method to also be used on Wind'ohs drives.

NB depending on the size of the partition, this command could take a while to complete.

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shred -vzu /tmp/junk-file-to-be-shredded
2009-06-18 12:00:19
User: mpb
Functions: shred
0
Up
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securely overwrite a file with random junk, rename it to clear the directory entry and finally delete it
Show sample output | Comments (2) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
<<<"k=1024; m=k*k; g=k*m; g" bc
2009-06-17 10:35:10
User: mpb
8
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Using bash inline "here document" with three less-than symbols on command line

There are two ways to use "here documents" with bash to fill stdin:

The following example shows use with the "bc" command.

a) Using a delimiter at the end of data:

less-than less-than eeooff bc

> k=1024

> m=k*k

> g=k*m

> g

> eeooff

1073741824

b) using the "inline" verion with three less-than symbols:

less-than less-than less-than "k=1024; m=k*k; g=k*m; g" bc

1073741824

One nice advantage of using the triple less-than version is that the command can easily be recalled

from command line history and re-executed.

PS: in this "description", I had to use the name "less-than" to represent the less-than symbol because the commandlinefu input text box seems to eat up the real less-than symbols. Odd.

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urpmi --auto-update --force # apply all pending updates (Mandriva Linux)
2009-03-28 14:59:26
User: mpb
0
Up
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Apply all pending updates to Mandriva Linux system (2008.0 and newer).

Update a Mandriva Linux system with any pending updates.

This command needs to be run with root privilege.

Using the "--force" option answers "yes" to any interactive prompts

thus allowing the updates to be left unattended to completion.

NB if there is an update for glibc and/or a new kernel then the system

would need to be rebooted for these to take effect.

A prerequisite for running "urpmi --auto-update" is to have correctly defined

urpmi media sources (which can be done by visiting http://easyurpmi.zarb.org/).

If there are no new updates the the message "Packages are up to date" is shown.

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pwgen
2009-03-28 11:43:21
User: mpb
6
Up
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Generate random passwords (from which you may select "memorable" ones)

See: "man pwgen" for full details.

Some Linux distros may not have pwgen included in the base distribution

so you maye have to install it (eg in Mandriva Linux: "urpmi pwgen").

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!}sort
2009-03-28 00:18:39
User: mpb
12
Up
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from within vi, pipe a chunk of lines to a command line and replace the chunk with the result

The vi key sequence !}command will send the file contents from the cursor

to the next blank line as STDOUT to the command specified

and replace that sequence of file lines with the output of the command.

For example: sorting a block of data - !}sort

The sequence !{command will do the same but "upwards" (from the current position towards the start of the file.

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netstat -atn | awk ' /tcp/ {printf("%s\n",substr($4,index($4,":")+1,length($4) )) }' | sed -e "s/://g" | sort -rnu | awk '{array [$1] = $1} END {i=32768; again=1; while (again == 1) {if (array[i] == i) {i=i+1} else {print i; again=0}}}'
2009-03-27 20:38:43
User: mpb
Functions: awk netstat sed sort
4
Up
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find an unused unprivileged TCP port

Some commands (such as netcat) have a port option but how can you know which ports are unused?

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# wc -l /var/log/security/writable.today
2009-03-19 12:25:52
User: mpb
Functions: wc
0
Up
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How many world writeable files on your system? (Mandriva Linux msec)

Mandriva Linux includes a security tool called "msec" (configurable via "draksec").

One of the many things it regularily checks for is world writeable files.

If any are found, it writes the list to /var/log/security/writable.today.

"wc -l" simply counts the number of lines in the file.

This number should be low.

Browse through /var/log/security/writable.today and consider if any of those files *need* to be world-writeable (and if not, modify the permissions. eg: "chmod o-w $file").

A large number of world-writeable files may indicate that umask is not correctly set in /etc/profile (or ${HOME}/.bash_profile) but could also indicate poor security configuration or even malicious activity.

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vos listvldb | agrep LOCKED -d RWrite | grep RWrite: | awk -F: '{print $2}' | awk '{printf("%s ",$1)} END {printf("\n")}'
2009-03-17 19:55:39
User: mpb
Functions: awk grep
0
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Display list of locked AFS volumes (if any)

This command shows if there are any locked AFS volumes.

The output is a list of AFS volume IDs (or nothing if there are none locked).

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rpm -qa --queryformat '%{installtime} \"%{vendor}\" %{name}-%{version}-%{release} %{installtime:date}\n' | grep "Thu 05 Mar"
2009-03-17 13:38:20
User: mpb
Functions: grep rpm
4
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Display a list of RPMs installed on a particular date

Find out which RPMs were installed on a particular date.

These would (naturally) include update RPMs.

This example shows searching for "Thu 05 Mar" (with grep).

Alternatively, pipe it to less so you can search inside less (with less's neat text highlighting of the search term):

rpm -qa --queryformat '%{installtime} \"%{vendor}\" %{name}-%{version}-%{release} %{installtime:date}\n' | less # (this example) search term: Thu 05 Mar

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play $audio_file
2009-03-17 11:30:02
User: mpb
-3
Up
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Play audio file

"play" is part of "SoX"

SoX - Sound eXchange, the Swiss Army knife of audio manipulation.

For details, see: man sox

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:!cp % %-
2009-03-17 00:34:24
User: mpb
5
Up
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Create a backup of file being edited while using vi

At the start of a vi session and *before* saving any changes use ":!cp % %-" to make a backup of the current file being edited.

example: vi /data/some/long/path/file

:!cp% %-

creates /data/some/long/path/file-

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# indicates a comment in shell
2009-03-16 23:15:33
User: mpb
-4
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#

Using the "#" in shell is surprisingly useful.

Some of the uses I found:

a) As a visible copy buffer in shell history (caveat: do not use for passwords :-)

b) To build complex commands until ready then hit the HOME, DEL, ENTER keys to run it

c) Placing reference data into shell history (search for tags with CTRL-R TAGNAME)

d) Putting aside a "work in progress" command to focus on another task (HOME # ENTER)

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rpm -qa --qf '%{SIZE} %{NAME}\n' | sort -nr | nl | head -6 # six largest RPMs
2009-03-15 22:18:17
User: mpb
Functions: head nl rpm sort
2
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Display 6 largest installed RPMs sorted by size (descending)

Low on disk space? Check the largest installed RPMs for delete canditates.

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ls -1 | grep " " | awk '{printf("mv \"%s\" ",$0); gsub(/ /,"_",$0); printf("%s\n",$0)}' | sh # rename filenames: spaces to "_"
2009-03-15 18:42:43
User: mpb
Functions: awk grep ls rename sh
2
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Convert embedded spaces in filenames to "_" (underscore)

This command converts filenames with embedded spaces in the current directory replacing spaces with the underscore ("_") character.

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gcal -K -q GB_EN 2009 # display holidays in UK/England for 2009 (with week numbers)
2009-03-15 10:19:52
User: mpb
5
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Display calendar with specific national holidays and week numbers

NB when you run this gcal command in your shell, holidays are highlighted

but this highlighting does not show in the sample output (above).

To find full details on gcal options: gcal --long-help | less

Example for United States, Pennsylvania:

gcal -K -q US_PA 2009 # display holidays in USA/Pennsylvania for 2009 (with week numbers)

Example for Hong Kong:

gcal -K -q HK 2009 # display holidays in Hong Kong for 2009 (with week numbers)

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