bash_script_some_more_tips.txt

BASH SHELL SCRIPTS TIPS:


#!/bin/bash -options (-x -i)

MATH:

var1=100;var2=200;var3=$(expr $var1 + $var2);echo "Total: $var3"
Total: 300

var1=100;var2=200;var3=$[$var1 + $var2];echo "Total: $var3"
Total: 300

VAR:

var_teste=1
var_year=$(date +%Y)
var1=$var2


If condition true/false or command (exit 0)
Then 
:
Else
Fi

If condition/command
Then 
:
Elif condition/command
Then
:
Elif condition/command
Then
:
Else 
:
Fi

Comparisons:

String:
[ x -eq y ] : x=y
[ x -ge y ] : x>=y
[ x -gty ] : x>y
[ x -le y ] : x<=y
[ x -lt y ] : x<y
[ x -ne y ] : x<>t

Numeric:

[ x = y ] : x=y
[ x !=y ] : x<>y
[ x < t] : x<y
[ x > y ] : x>y
[ -n y ] : not zero
[ -z y] : zero


File teste:

If [ -d $file ]
Then

-d file = exist and dir
-e file = exist
-f file = exist and file
-r file = exist and perm read
-s file = exist and not empty
-w file = exist andperm write
-x file = exist and perm exec
-O file =  exist and owned by user
-G file = exist and owned by group
file1 -nt file2 = file1 newer file2
file1 -ot file2 = file1 older file2

Conditional Compound:

[ condition ] && [ condition ] = AND
[ condition ] || [ condition ] = OR


Test var zero or null:

If [ -n $VAR ] # var is not null

If [ -z $VAR ] # var is empty 


Looping Specific Commands:

while/until
do
	break (get out single looping). One break is needed for each nested looping
	continue (skip commands above and go back do do
done

Linux Shell Scripts: for

for i in *; do qemu-img info "$i"; done
for i in *.txt; do echo "hello $i"; done
for i in teste* ; do cp $i /tmp/ ; done

while read i; do echo $i; done < teste.txt

for i in $(cat peptides.txt); do echo $I; done

sort -d teste.txt | uniq -d

cp -i alex.txt ../teste2/ <<< "n

for z in *.zip; do cp -i $z /userdata/roms/neogeo <<< "n; done
for word in $(cat peptides.txt); do echo $word; done

i=0
while [ $i -lt 10 ]; do echo "valor: $i" ; i=$[$i+1]; done;


while read -r line; 
do 
   echo "$line" ;
done < input.file

cat /etc/passwd | while read LREAD
do
    echo ${LREAD}
done