Intro To 'printf' Command In Linux

2023-06-10 - By Robert Elder

     I use the 'printf' command to print formatted strings:

printf '%s %i %u %%.\n' 'Hello World!' -1 1

Hello World! -1 1 %.

The 'printf' Function Vs. 'printf' Shell Command

     The 'printf' command can be thought of as a thin wrapper around the 'printf' function from the C Standard Library.

     The 'printf' command is capable of printing formatted strings of text in ways that are more advanced than the echo command:

printf 'First: %c Second: %d Third: %s.\n' 'p' 123 "Hello"

First: p Second: 123 Third: Hello.

     The first argument to the 'printf' command is the format string to print, where the percentage signs indicate the location where arguments will be substituted.  This is followed by zero or more arguments.

Example Format Strings With 'printf'

     The 'printf' command supports floating point numbers with flags that control the format and precision:

printf "My favourite floating point number: '%.2f'.\n" 420.69
printf "My favourite floating point number: '%.10f'.\n" 420.69

My favourite floating point number: '420.69'.
My favourite floating point number: '420.6900000000'.

     It also supports signed and unsigned integers:

printf "%u\n" -1

18446744073709551615

printf "%i\n" -1

-1

printf "0x%X\n" 3735928559

0xDEADBEEF

     characters:

printf "My favourite octal characters: '%b' '%b' '%b'.\n" "\0141" "\0142" "\0143"

My favourite octal characters: 'a' 'b' 'c'.

     strings:

printf "My favourite string: '%s'.\n" "Linux"

My favourite string: 'Linux'.

     and many more.

Shell Builtin Vs. Executable

     The 'printf' command can be implemented separately as a shell builtin or independently as a standalone application.  Therefore, the exact behavior of the 'printf' command could depend on which version you end up using:

type -a printf

printf is a shell builtin
printf is /usr/bin/printf
printf is /bin/printf

     See the 'info' pages for more information about the differences between the builtin and shell 'printf' functions:

info printf

...
   Due to shell aliases and built-in ‘printf’ functions, using an
unadorned ‘printf’ interactively or in a script may get you different
functionality than that described here.  Invoke it via ‘env’ (i.e., ‘env
printf ...’) to avoid interference from the shell.
...

     And that's why the 'printf' command is my favourite Linux command.