Some useful text manipulation commands (sed, gawk, etc.)

text.sh

# print the number of columns 
gawk '{print NF}' file | sort -nu | tail -n 1
# Use head -n 1 for lowest column count, tail -n 1 for highest column count.

# print columns
gawk '{print $0}' file        # all columns
gawk '{print $4}' file        # 4th column
gawk -F "," '{print $2}' file # specific separator

# split a string with a delimiter into lines
echo "string1:string2:string3:string4:string5" | sed s/:/\\n/g

# remove first line from a file
sed '1d' file.txt > tmpfile; mv tmpfile file.txt # POSIX
sed -i 's/original_regex/new_regex/g' file.txt   # replace text within a file
sed -i.bak '/pattern to match/d' file.txt        # remove lines with matched pattern
sed -i '1d' file.txt                             # GNU sed only, creates a temporary file
sed 's/.*/&&/g' file.txt > file.enum             # duplicate matched pattern

paste -d, a.csv b.csv         # merge lines of many files