The printf command of the shell tutorial

In the previous section we learned about the Shell's echo command, which we'll learn from the Shell's other output command printf.

The printf command mimics the printf () program in the C library.

printf is defined by the POSIX standard, so scripting with printf is better than using echo portability.

printf uses reference text or space-delimited parameters, which can be used outside of the format string in printf, as well as the width of the string, left and right alignment, and so on. Default printf does not automatically add line breaks like echo, we can add \ n manually.

The syntax of the printf command:

printf  format-string  [arguments ...]

Parameter description:

• format-string: Controlling strings for formatting
• arguments: as a parameter list

Instance:

printf "%-10s%-8s%-4s\n" name sex weight kg  

Execution Result:

[[email protected] bin]#/test.sh name     sex   weight kg Guo jing     male      66.12 yang over     male      48.65 Guoff     female      47.99

%s%c%d%f are format alternates

%-10s refers to a width of 10 characters (-for left alignment, not to right-aligned), any character will be displayed in 10 character justifies characters, if not enough is automatically filled with spaces, more than will also show the content.

%-4.2F refers to the format of decimals, where. 2 refers to 2 decimal places reserved.

More examples:

Execution Result:

1 ABC1 Abcabcdefabcdefabcdefa b CD e fg H IJ and   0

Escape sequences for printf

sequence	Description
\a	A warning character, usually an ASCII bel character
\b	Back off
\c	Suppresses (does not display) the newline character at any end of the output (only valid in the parameter string under the control of the%b format designator), and any characters left in the argument, any subsequent arguments, and any characters left in the format string are ignored
\f	Page Change (formfeed)
\ n	Line break
\ r	Enter (carriage return)
\ t	Horizontal tab
\v	Vertical tab
\\	A literal backslash character
\ddd	A character that represents an octal value of 1 to 3 digits. Valid only in format strings
\0ddd	Represents octal value characters from 1 to 3 bits

Shell Tutorial's printf command