id

If no user operand is provided, the id utility shall write the user and group IDs and the corresponding user and group names of the invoking process to standard output. If the effective and real IDs do not match, both shall be written. If multiple groups are supported by the underlying system (see the description of {NGROUPS MAX} in the System Interfaces volume of POSIX.1-2017), the supplementary group affiliations of the invoking process shall also be written. If a user operand is provided and the process has appropriate privileges, the user and group IDs of the selected user shall be written. In this case, effective IDs shall be assumed to be identical to real IDs. If the selected user has more than one allowable group membership listed in the group database, these shall be written in the same manner as the supplementary groups described in the preceding paragraph. Output all different group IDs (effective, real, and supplementary) only, using the format "%u n". If there is more than one distinct group affiliation, output each such affiliation, using the format " %u", before the is output. 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 and informative messages written to standard output. [XSI) ] ![[Option Start]]( Determine the location of message catalogs for the processing of LC MESSAGES. ![[Option End]]( The following formats shall be used when the LC MESSAGES locale category specifies the POSIX locale. In other locales, the strings uid , gid , euid , egid , and groups may be replaced with more appropriate strings corresponding to the locale. When any of the options are specified, the output format shall be as described in the OPTIONS section. Output produced by the -G option and by the default case could potentially produce very long lines on systems that support large numbers of supplementary groups. (On systems with user and group IDs that are 32-bit integers and with group names with a maximum of 8 bytes per name, 93 supplementary groups plus distinct effective and real group and user IDs could theoretically overflow the 2048-byte {LINE MAX} text file line limit on the default output case. It would take about 186 supplementary groups to overflow the 2048-byte barrier using id -G ). This is not expected to be a problem in practice, but in cases where it is a concern, applications should consider using fold -s before post-processing the output of id .