bash Cheatsheet

1. read line from file

 

#!/bin/bash
#
#example: my_read_file.sh input.csv
#

max_level=0
max_line=""

#loop read line
while read line || [ -n "$line" ]
#read line not end with '/n'
do

elements=(${line//|/ })
# IFS='|' read -a elements <<< "$line"
index_last=${#elements[@]}-1
level="${elements[$index_last]}"

#max level
if [ $level -gt $max_level ]
then
max_level=$level
max_line=$line
fi

done < "$1"

echo "$max_line"

 

2. sample

#/bin/bash
#
#usage: bash_sample.sh hello wolrd sample_file.csv

#read from typing
var_a1=$1
var_a2=$2
echo "${var_a1} ${var_a2}"

while read line || [ -n "$line" ]
do
elements=(${line//|/ })
len=${#elements[@]}
last_element=${elements[$len-1]}

if [ $last_element -gt 4 ]
then
echo $last_element
else
echo "not condition"
fi
done < $3

path_output="./output.txt"
rm "${path_output}"
#echo "test" >> "${path_output}"
cat $3 >> "${path_output}"

#current folder
for d in `ls ./`; do
echo ${d}
done

#parent folder
for d in `ls ../`; do
echo ${d}
done

 

 

 3. merge files

cat ./* > bigfile.sql