Table of Contents

Prototype: format(string, ...)

Return type: string

Description: Applies sprintf-style formatting to a given string.

This function will format numbers (o, x, d and f) or strings (s) but not potentially dangerous things like individual characters or pointer offsets.

The %S specifier is special and non-standard. When you use it on a slist or a data container, the data will be packed into a one-line string you can put in a log message, for instance.

This function will fail if it doesn't have enough arguments; if any format specifier contains the modifiers hLqjzt; or if any format specifier is not one of doxfsS.


body common control
      bundlesequence => { "run" };

bundle agent run
      "v" string => "2.5.6";
      "vlist" slist => splitstring($(v), "\.", 3);
      "padded" string => format("%04d%04d%04d", nth("vlist", 0), nth("vlist", 1), nth("vlist", 2));
      "a" string => format("%10.10s", "x");
      "b" string => format("%-10.10s", "x");
      "c" string => format("%04d", 1);
      "d" string => format("%07.2f", 1);
      "e" string => format("hello my name is %s %s", "Inigo", "Montoya");

      "container" data => parsejson('{ "x": "y", "z": true }');

      "packed" string => format("slist = %S, container = %S", vlist, container);

      "version $(v) => padded $(padded)";
      "%10.10s on 'x' => '$(a)'";
      "%-10.10s on 'x' => '$(b)'";
      "%04d on '1' => '$(c)'";
      "%07.2f on '1' => '$(d)'";
      "you killed my father... => '$(e)'";


R: version 2.5.6 => padded 000200050006
R: %10.10s on 'x' => '         x'
R: %-10.10s on 'x' => 'x         '
R: %04d on '1' => '0001'
R: %07.2f on '1' => '0001.00'
R: you killed my father... => 'hello my name is Inigo Montoya'
R: slist = { "2", "5", "6" }, container = {"x":"y","z":true}

Note: the underlying sprintf system call may behave differently on some platforms for some formats. Test carefully. For example, the format %08s will use spaces to fill the string up to 8 characters on libc platforms, but on Darwin (Mac OS X) it will use zeroes. According to SUSv4 the behavior is undefined for this specific case.