BASH TIPS & TRICKS

  Compiled by campmany since 2001
  Latest version of this file available at: 
  http://www.ecampmany.com/txt/help.txt
 


SYSTEM ADMINISTRATION:

# Display Linux version
cat /proc/version

# Display Linux distribution
cat /etc/issue

# Display IP
hostname -I

# Display 32/64 bits
file /sbin/init

# List printers available
lpstat -a

# Execution time
time ./script

# Install MSI file in Linux
wine msiexec /i file.msi

# Check if file exists
if [ -f $file ]; then

# List directories only
ls -d */

# Find matching files
find . -exec grep -Hn hello {} \;

# List files absolute path
find `pwd` . -type f 

# Trash folder in Ubuntu
/home/username/.local/share/Trash


TEXT MANIPULATION:

# Delete return carriage
awk '{sub(/\x0d/,"");print}'

# Delete empty lines
sed '/^$/d'

# Delete blank lines with spaces
sed '/^ *$/d'

# Delete duplicate lines
awk '!seen[$0]++' $file

# Delete N first characters
cut -c N- $file

# Delete 1st col with diff length (tabs)
cut -f 2-$NF

# Skip header with n lines
sed 1,nd 

# Delete last line
sed '$d'

# Replace multiple spaces by tabs
tr -s " " "\t" 

# Replace only line n
sed -i 'n s/match/new/' file

# Echo with no return
echo -e "Hi"\c

# Use value of variable  
file=${!num}

# Substring
substring=${string:0:6}

# String length
${#string}

# Uppercase to lowercase
awk {'print tolower($_)'}

# Translate from Latin-1 to ascii
iconv -f ISO-8859-1 -t ascii//TRANSLIT

# Join two files with same 1st column
join 1.txt 2.txt 

# Join two files by columns 
paste 1.txt 2.txt

# Check if "string" is in $list
list="This is Mystring"
if [[ $var == *"string"* ]]

# Check if $var is in $list
list="11 22 33"
if [[ $list =~(^| )$var($| ) ]]

# Print matching line and previous
grep -B1 string file


NUMERICAL CALCULATION:

# 2 digit number loop (bash)
for i in {01..99}

# N increment loop
for i in `seq 0 n 100`; 

# N increment index 
num=$[$num + n]

# Sum all values in a row 
awk '{for (i=1; i<=NF; i++) sum[NR]+= $i; 
print sum[NR]}'

# Sum and average of 1st col:
awk '{ s += $1 } END  { print s, s/NR }'

# Sum 3rd col every k rows:
awk '{s+=$3}NR%k==0 { print s; s=0 }'

# Find max and min 1st col
awk 'NR == 1 {m=$1 ; p=$1}
$1 >= m {m = $1}
$1 <= p {p = $1}
END { print "Max = " m, "   Min = " p }'

# Round or truncate
echo .6 | awk '{printf "%0.f %d\n",$1,$1}'

# Degrees.minutes to decimal coordinates
awk '{split($1,a,".");print a[1]+a[2]/60}

# Read (H)H:MM, print HHMM
awk 'sub(/:/,"") {printf "%04d \n",$2}'

# Read YYYY/(M)M/(D)D (H)H:MM
awk '{split($1,a,"/")split($2,b,":"); 
printf "%4d%02d%02d %04d\n", a[3],a[2],a[1],b[1]b[2]}'

# Transform YYYYMMDD to JJJ
date -d "YYYYMMDD" +%j

# Loop over time
startdate=YYYYMMDD
finaldate=yyyymmdd
tday=$startdate
while [  $tday -lt $finaldate ]; do
tday=$(date +%Y%m%d -d "$tday 1 day") 
done 


OTHER:

# Display help/error message
if [ $# -lt 3 ]; then
echo "3 inputs expected" >&2; exit 1
fi

# Check Max file size allowed in UNIX system
dd if=/dev/zero bs=1000000 count=3000 of=./largefile
ls -l largefile

# Join images vertically
convert o.png o.png -append 8.png 

# Join images horizontally
convert o.png o.png +append oo.png

# Merge multiple PDF:
gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=out.pdf -dBATCH 1.pdf 2.pdf
convert -density 150 pdf1.pdf pdf2.pdf out.pdf

# Split PDF into pages:
pdftk in.pdf burst

# Reduce PDF size:
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf
(screen/ebook/printer/prepress)

# Hardprint ASCII file double page:
enscript -2rG -Pprinter filename
a2ps -P printer filename

# Select by columns 
ctrl + mouse

# Some vi commands 
Join: J
Redo: .
Delete everything below: +,$d