Shell

Manipulating Files and Directories

pwd: print the current working directory as an absolute path.
ls: list the contents of the current directory.
cd: change into the directory you specify.

cd ..   # move to the parent directory
cd ~    # jump to your home directory
cd .    # stay in the current directory

cp: copy files.

cp source_file destination_file

mv: move or rename files.
rm: remove files.
rmdir: remove a directory.
mkdir: create a directory.

Manipulating Data

cat: print the contents of a file.
less file: view a file one page at a time.

• :n : next page.
• :q : quit.

head: print the first 10 lines of a file.
Tab completion helps fill in filenames quickly.

head -n <number_of_lines> filename

ls -R      # list every file and directory below the current location
ls -R -F   # same, and mark entries by type

man <command>    # open the manual page for a command

tail -n +k filename    # show the file from line k to the end

cut -f 2-5,8 -d , values.csv   # select columns 2 through 5 and column 8

history    # display your shell history

grep <pattern> <filename>
# -c : count matching lines
# -h : suppress filenames in the output
# -i : ignore case
# -l : print only filenames that match
# -n : include line numbers
# -v : show non-matching lines

Combining Tools

Use the pipe operator | to connect commands.

tail -n 5 seasonal/winter.csv > /home/repl/last.csv   # redirect output into a file
tail -n 2 seasonal/winter.csv > bottom.csv

cut -d , -f 2 seasonal/summer.csv | grep -v Tooth

cut -d , -f 2 seasonal/summer.csv | grep -v Tooth | head -n 1

# wc : word count (-c characters, -w words, -l lines)

grep 2017-07 seasonal/spring.csv
# 2017-07-10,incisor
# 2017-07-16,bicuspid
# 2017-07-23,bicuspid

grep 2017-07 seasonal/spring.csv | wc
#       3       3      59

grep 2017-07 seasonal/spring.csv | wc -l
# 3

cut -d , -f 1 seasonal/*
cut -d , -f 1 seasonal/*.csv
cut -d , -f 1 seasonal/winter.csv seasonal/spring.csv seasonal/summer.csv seasonal/autumn.csv

cut -d , -f 2 seasonal/winter.csv | grep -v Tooth | sort -r

cut -d , -f 2 seasonal/winter.csv | grep -v Tooth | sort | uniq -c   # remove duplicates and count them

Ctrl + C: stop a running command.

wc -l seasonal/*.csv | grep -v total | sort -n | head -n 1

Batch Processing

echo $OSTYPE
# linux-gnu

testing=seasonal/winter.csv    # no spaces when assigning shell variables
head -n 1 $testing

Use loops to process sets of files.

for filetype in docx odt pdf; do echo $filetype; done

for filename in people/*; do echo $filename; done

datasets=seasonal/*.csv
for filename in $datasets; do echo $filename; done

for file in seasonal/*.csv; do grep 2017-07 "$file" | tail -n 1; done

Creating New Tools

• Ctrl + K: delete a line.
• Ctrl + U: restore the deleted line.
• Ctrl + O: save the file (press Enter to confirm the filename).
• Ctrl + X: exit the editor.

nano dates.sh
# inside nano: cut -d , -f 1 seasonal/*.csv
bash dates.sh
bash dates.sh