nice

The nice utility shall invoke a utility, requesting that it be run with a different nice value (see XBD Nice Value ). With no options, the executed utility shall be run with a nice value that is some implementation-defined quantity greater than or equal to the nice value of the current process. If the user lacks appropriate privileges to affect the nice value in the requested manner, the nice utility shall not affect the nice value; in this case, a warning message may be written to standard error, but this shall not prevent the invocation of utility or affect the exit status. A positive or negative decimal integer which shall have the same effect on the execution of the utility as if the utility had called the nice () function with the numeric value of the increment option-argument. Provide a default value for the internationalization variables that are unset or null. (See XBD Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) If set to a non-empty string value, override the values of all the other internationalization variables. Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. [XSI) ] ![[Option Start]]( Determine the location of message catalogs for the processing of LC MESSAGES. ![[Option End]]( The utility specified by utility was found but could not be invoked. On some implementations they have no discernible effect on the invoked utility and on some others they are exactly equivalent. The command , env , nice , nohup , time , and xargs utilities have been specified to use exit code 127 if an error occurs so that applications can distinguish "failure to find a utility" from "invoked utility exited with an error indication". The value 127 was chosen because it is not commonly used for other meanings; most utilities use small values for "normal error conditions" and the values above 128 can be confused with termination due to receipt of a signal. The value 126 was chosen in a similar manner to indicate that the utility could be found, but not invoked. Some scripts produce meaningful error messages differentiating the 126 and 127 cases. The distinction between exit codes 126 and 127 is based on KornShell practice that uses 127 when all attempts to exec the utility fail with [ENOENT], and uses 126 when any attempt to exec the utility fails for any other reason. When a user without appropriate privileges gives a negative increment , System V treats it like the command nice -0 utility , while 4.3 BSD writes a "permission denied" message and does not run the utility. The standard specifies the System V behavior together with an optional BSD-style "permission denied" message. The term "utility" is used, rather than "command", to highlight the fact that shell compound commands, pipelines, and so on, cannot be used. Special built-ins also cannot be used. However, "utility" includes user application programs and shell scripts, not just utilities defined in this volume of POSIX.1-2017. Some historical documentation states that the increment value must be within a fixed range. This is misleading; the valid increment values on any invocation are determined by the current process nice value, which is not always the default. The definition of nice value is not intended to suggest that all processes in a system have priorities that are comparable. Scheduling policy extensions such as the realtime priorities in the System Interfaces volume of POSIX.1-2017 make the notion of a single underlying priority for all scheduling policies problematic. Some implementations may implement the nice -related features to affect all processes on the system, others to affect just the general time-sharing activities implied by this volume of POSIX.1-2017, and others may have no effect at all. Because of the use of "implementation-defined" in nice and renice , a wide range of implementatio