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Sammlung nützlicher Befehle

General Tool Commands


fetch all git branches and prune remotely deleted branches

git remote update origin --prune

man git-remote

delete all files and directories in a Git work tree which are under gitignore (e.g. for removing builds)

get number of commits in a Git repository

## total number (in all branches)
git rev-list --all | wc -l
## number per committer
git shortlog -s -n --all

man git-rev-parse man git-shortlog

show predefined macros of a compiler

gcc -dM -E -x c /dev/null
g++ -dM -E -x c /dev/null
clang -dM -E -x c /dev/null
clang++ -dM -E -x c /dev/null


show details for a certificate file

# certificate has PEM format (Pretty Enhanced Mail)
openssl x509 -in cert-file.pem -text -noout -fingerprint
# certificate has DER format (Distinguished Encoding Rules)
openssl x509 -inform der -in cert-file.cer -text -noout -fingerprint

man x509

show details for a private key file

openssl rsa -in privkey.pem -text -noout

man rsa

show details of a certificate signing request

openssl req -in csr.pem -noout -text

man req

extract certificate and private key from PKCS#12 file

openssl pkcs12 -in yourP12File.pfx -clcerts -nokeys -out publicCert.pem
openssl pkcs12 -in yourP12File.pfx -nocerts -out privateKey.pem

man pkcs12

create a self-signed certificate

openssl genrsa -out privKey.pem
openssl req -new -x509 -key privKey.pem -out cert.pem

man genrsa man req

AES-256-CBC benchmark

## with AES-NI (if available)
openssl speed -evp aes-256-cbc
## without AES-NI
OPENSSL_ia32cap="~0x200000200000000" openssl speed -evp aes-256-cbc
## multithread
openssl speed -multi 2 -evp aes-256-cbc

man speed

parse a file's ASN.1 content

openssl asn1parse -in someCertOrKeyOrOther.pem

man asn1parse

Network Stuff

test a proxy server

curl -x <[protocol://][user:password@]proxyhost[:port]> | w3m -dump -T text/html
# for Squid running on localhost that's:
curl -x | w3m -dump -T text/html


measure duration of HTTP request

curl -w %{time_connect}:%{time_starttransfer}:%{time_total}


check whether a TCP connection can be established with a three second timeout

nc -w3 -z 80 ## return code zero on success


mDNS query

dig somehostname.local @ -p 5353


verify DNSSEC chain of a domain

## if you don't have the root keys yet, obtain them first
unbound-anchor -a /usr/local/etc/unbound/root.key
## if the root key file is at the standard path of your unbound/ldns installation, the "-k" option can be omitted
drill -S -k /usr/local/etc/unbound/root.key
## if your resolver does not support DNSSEC, use a public one, e.g. Hurricane Electric
drill -S -k /usr/local/etc/unbound/root.key @

drill(1) unbound-anchor(8)

check whether your DNS resolver discards invalid DNSSEC domains



check whether your DNS resolver uses QNAME minimisation

dig txt +short


scan all TCP ports of a host

nmap -p-


reverse DNS lookup of an IP subnet

nmap -R -sL
nmap -R -sL -6 2001:db8::43a1:89d0/124


scan for responding hosts in an IP subnet

## probe TCP connect on Port 80 with five attempts for each host
## probe ICMP with five attempts for each host
nping --icmp
## probe ICMP with one attempt for each host and 200ms between requests (and decrease verbosity)
nping -q --count 1 --delay 200ms --icmp


File Stuff

count lines of a certain file type recursively (e.g. C++ source files)

find /your/dir -name "*.cpp" -print0 | xargs -0 wc -l

find(1) xargs(1)

find /your/dir -type l ! -exec test -e {} \; -print


delete recursively all files with a certain name (e.g. “.DS_Store”)

find /your/dir -type f -name .DS_Store -print -delete


create checksums of directory tree and verify them

# create checksums of directory tree
rhash -r --md5 /backups/ > /tmp/backups.md5
rhash -r --crc32 /backups/ > /tmp/backups.sfv
# check one file containing MD5 hashes
rhash -c /tmp/backups.md5
# check all SFV, MD5 and SHA-256 files in directory tree
rhash -cr --crc-accept=sfv,md5,sha256 /tmp/directory/


create a file with specific timestamps

touch -a -m -t 202612180130.09 fileName.ext
## -a = accessed
## -m = modified
## -t = timestamp - use [[CC]YY]MMDDhhmm[.ss] time format


handle sparse files

## create a 100 GiB sparse file
truncate -s 100G fileName.ext
## copy sparse files (works also from/to block devices; 4k should match the block size used within you sparse file)
dd if=inputSparse.ext of=outputSparse.ext bs=4096 conv=sparse

truncate(1) dd(1)

create a 7-ZIP archive encrypted with a password

7z a -p -mhe=on the_new_archive.7z -r dir_containing_stuff another_file.bin


Disk and Partition Stuff

show information about partitions of disks (on Linux)

file -s /dev/sd*

disk images over SSH

## from a local disk send compressed image to remote host
dd if=/dev/sda bs=1048576 | pv | lz4 | ssh "dd of=/backup/basil-sda.img.lz4"
## to a local disk receive compressed image from remote host
ssh "cat /backup/basil-sda.img.lz4" | lz4cat | pv | dd of=/dev/sda bs=1048576

Conversion Stuff

convert image file using ImageMagick

## make a big image small
convert big_input.tif -resize 256x256 small_output.png
## make an image grayscale and remove any transparency
convert input.png -alpha deactivate -colorspace Gray output.png
## create PNG with transparency from SVG, determine it's pixel dimensions from a DPI parameter
convert -background none -density 1200 input.svg output.png
## create PNG with transparency from SVG, specify it's pixel dimensions directly
convert -background none -size 512x512 input.svg output.png

convert(1) ImageMagick(1)

batch convert images in a directory: rename by creation date and resize to width

### for JPGs
exiftool -ext jpg '-FileName<CreateDate' -d %Y%m%d_%H%M%S%%-c.%%e .
mogrify -resize 375 -define preserve-timestamp=True *.JPG
### for PNGs
exiftool -ext png '-FileName<DateCreated' -d %Y%m%d_%H%M%S%%-c.%%e .
mogrify -resize 375 -define preserve-timestamp=True *.PNG
### Comments:
## the "%%-c" in the filename template is for a numerical suffix, in case of multiple images with the same date
## the "-define preserve-timestamp=True" is for keeping file attributes for timestamps
## for case-sensitive filesystems in the "mogrify" command the glob pattern must be adjusted

exiftool(1) mogrify(1) ImageMagick(1)

Unix timestamp to human readable time

## with BSD date
date -r 1523210382
## with GNU date
date -d @1523210382

date(1) from BSD — date(1) from GNU

format XML

## prettify XML (proper indentation)
xmllint --format input_ugly.xml > output_pretty.xml
## uglify XML (remove unnecessary whitespace)
xmllint --noblanks input_pretty.xml > output_ugly.xml


C array of the content of some file

xxd -i someFile.bin


change the character encoding of a file‘s content

## convert from "UTF-8" to "ISO-8859-1"
recode utf8...latin1 test.dat 
## autodetect and convert to "ISO-8859-1"
recode ..latin1 test.dat
## list available encodings available in your "recode" build
recode --list

recode(1) (more lightweight and probably already installed alternative: iconv(1))

occurrences of non-ASCII characters in a file‘s content (with GNU grep)

ggrep --color='auto' -P -n "[\x80-\xFF]" file.txt

occurrences of invalid UTF-8 characters in a file‘s content (this assumes you have an UTF-8 locale set)

grep -axv '.*' file.txt

some StackOverflow discussion

count how many time each byte value occurs in a file‘s content

recode latin1/..count-characters < input.dat


Process Stuff

execute a program in a background terminal

## create named session using the terminal emulator "screen"
screen -dMS some_session_name /usr/bin/command command_args
## show PID of the "screen" session
screen -lsS some_session_name | awk '/\.some_session_name\t/ {print $1}' | cut -d. -f1
## attach to the session
screen -rS some_session_name

show child PIDs of a PID

pgrep -P 56789

Bourne Again Shell

delete entries from the command history (e.g. to remove passwords)

## show the current history
## determine the entry number, in this example the desired entry was #501
history -d 501

avoid history recording for one interactive shell completely

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commands-general-tools.1588860913.txt.gz · Zuletzt geändert: 2020/05/07 16:15 von alex