Shell Common Command Summary (iii)

1.1. usage of the Cut command in the shell

The first usage is similar to awk, as shown in awk below :

Cat/etc/passwd|awk-f: ' {print $1,$5} '

Cut-d: The colon after-F 1,5/etc/passwd/-d indicates the delimiter between the fields, and-f indicates which fields after the de-delimiter

You can also use the cut command to cut partial characters with a scalar number of characters, which is implemented with the- C option and cannot coexist with the- d option.

Cut-c 1-4/etc/passwd # takes the first 1-4 characters of each line

1.2. Return line break

line break in Windows system is CRLF, English is carriage-return(enter \ r) Line-free (line break \ n ). So, when a shell script written by the Windows system runs on Linux , a transformation is required. Otherwise it will report a grammatical error "syntax error near unexpected token"

1.3. double quotes after Echo

Without double quotes, special variables are escaped with special symbols in the output variable, such as:

(1) for I in 2 \*;d o echo $i;d one;

(2) for I in 2 \*;d o echo "$i";d one;

The first statement does not display an asterisk, which represents all files in the current directory. Instead, you should use the second usage.

Shell Common Command Summary (iii)