Tips for Shell

Tips for Shell

There'll is some case-based tips for Shell.

1. Replace The sequence space with newline

Input Example

a b  c   d

Output Example

abcd

Summary

sedis the best solution.

Solution

sed -r -e ‘s/[[:space:]]/\n/g‘

2. Sort the unordered word list (with duplication) by frequencysummary

It is very useful when counting word frequency.

Solution

sort | uniq -c | sort -rn

3. AWK print line without first columnsummary

This command actually clear the first column from the file.

Solution

awk ‘{$1=""; print $0}‘

4. Show the longest line in the Filesummary

Taking advantage of the const in lengthawk

Solution

awk ‘{print $0" "length}‘ | sort -k2 -nr | head -1

5. Ignore line, match some patternsummary and solution

Using

grep -v

6. batchly Replace Namespacesummary

Using to loop over the file and to for sed perform the replacement.

Solution

for f in `find ./src -type f`; do sed -i ‘s/oldnamespace/newnamespace‘ $f; done

7. Generate, ..., sequencesummary

PerlCan be a better solution.

Solution

perl -e ‘for{$i=2;$i<=24;$i++}{printf("%02d\n", $i)}‘

8. Command Line Calculatorawk Solution

awk ‘{print 1/10}‘

and additional enter is needed

Perl Solution

More flexiable (with formatting).

perl -e ‘printf("%f\n", 1./10);‘

Tips for Shell