SHELL
FIND command
1. Find all files modified in last two days
find . -type f -mtime 2 -name *
2. Find all files modified in last two minutes
find . -type f -mmin 2 -name *
3. Find all files accessed in last two minutes
find . -type f -amin 2 -name *
4. Find all files whose status changed in last two minutes
find . -type f -cmin 2 -name *
5. Find all files whose timestamp is later than file "a.py"
find . -type f -newer "a.py" -name *
6. Find all files with skipping two depth from current directory
find . -type f -mindepth 2 -name *
7. Find all files within 2 directory depth
find . -type f -maxdepth 2 -name *
8. Find all files excluding few directories
find . -type f -name "*" \(-path <dir1> -o -path <-dir2> \) -prune -o -print
9. Find file files after certain date and time
To list out all files whose time stamp is after certain date and time, use the following.
touch ref_time.temp -t YYMMDDHHMM.SS
find DIR -type f -newer ref_time.temp -name "*"
GREP command
1. Char invariant, invert match, file name only
grep -i -v -l <match> *
2. Same as above i.e. -L does -v -l
grep -i -L <match> *
3. Count the number of match
grep -i -v -c <match> *
4. Stop after 7 matches
grep -m 7 <match> *
5. Print only matched part of string
grep -o <match> *
6. If one match is found updates status and exit
grep -q <match> *
7. Silent mode, no messages
grep -s <match> *
8. one line after match
grep -A 1 <match> *
9. one line before match
grep -B 1 <match> *
10. one line after and before match
grep -C 1 <match> *
11. Exclude file abc.pl in search
grep -C 1 --exclude=abc.pl <match> *
12. Exclude from file abc.pl in search i.e. content of file abc.pl is used as list of files to exclude
grep -C 1 --exclude-from=abc.pl <match> *
13. Exclude directory abc in search
grep -C 1 --exclude-dir=abc <match> *
14. Include file abc.pl in search i.e. search in only files named abc.pl
grep -C 1 --include=abc.pl <match> *
15. Print only matched part of string
grep -color=always <match> *
CUT - command
1. Get the nth character in the file
cut -cn <file>.<ext>
2. Get the nth field of the file i.e. nth column
cut -d'-' -fn <file>.<ext>
3. Get multiple fields
cut -d'-' -fn-m,o <file>.<ext>
4. Change output delimiter
cut -d'-' -fn-m,o --output-delimiter=':' <file>.<ext>
SORTED DIFF
To perform a sort on files before diff use the command below.
bash -c 'diff <(sort File1) <(sort File2)'
Rename all files in the directory
To rename all files with a particular search string with replace string use the "rename command".
Syntax: rename <search_string> <replace_string> files
>> ls
ddr3.sv ddr3.svh ddr3.csh
>> rename ddr3 ddr4 *
>> ls
ddr4.sv ddr4.svh ddr4.csh
Recording Shell (All stdin, stdout, stederr)
To record the linux shell completely instead of redirecting individual command we can use the "script" utility.
>>script
Script started, file is typescript
>> Command 1
Result 1
>> Command 2
Result 2
>> exit
Script done, file is typescript
The content Command 1, Result 1, Command 2 and Result 2 will be written to a file "typescript".
This is similar to PERL's "select" utility.
IFS (BASH)
The Inter Field Separator is used by BASH shell to separate fields (similar to delimiter in other utilities).
IFS=-
mystring="a-b c d"
for word in $mystring; do
echo "Word: $word"
done
# Set IFS to new line to pick up line by line
IFS=$'\n'
for word in `cat temp`; do
echo "Word: $word"
done
Command line calculator
"bc" is a command line utility which is used as a calculator.
e.g.:
bc
1+1
2
CTRL+D
It can also be used in pipe as follows,
echo 'ibase=16; FF' | bc
A good alias will be,
alias hex2dec "echo 'ibase=16; \!:*' | bc"