Do’s and Dont’s in shell scripting

1) Dont use Grep and Cat command together

Wrong way :

1

$cat filename | grep "pattern"

Correct way :

1

$grep "pattern" filename

2) Dont use cat,grep and wc commands together

Wrong way :

To count the number of occurence

1

$cat filename | grep "pattern" | wc -l

Correct way :

1

$grep -c "pattern" filename

3) dont use sort and uniq together ( to eliminate the duplicate entires )

Wrong way :

1

$sort filename | uniq

Correct way :

1

$sort -u filename

4) Dont use grep and awk together

wrong way :

1

$ grep "pattern" filename | awk '{print $1}'

correct way :

1

$ awk '/pattern/ {print $1}' filename

5) Dont use ls in for loop ( to manipulate the files )

wrong way :

1
2

for i in `ls` ; do echo $i; done
for i in `ls *.txt`; do echo $i; done

Correct way :

1
2

for i in *; do echo $i; done
for i in *.txt; do echo $i; done