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34 .\" @(#)getlogin.2 8.1 (Berkeley) 6/9/93

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36 .Dd June 9, 1993

37 .Dt GETLOGIN 2

38 .Os BSD 4.2

39 .Sh NAME

40 .Nm getlogin ,

41 .Nm setlogin

42 .Nd get/set login name

43 .Sh SYNOPSIS

44 .Fd #include <unistd.h>

45 .Ft char *

46 .Fo getlogin

47 .Fa void

48 .Fc

49 .Ft int

50 .Fo setlogin

51 .Fa "const char *name"

52 .Fc

53 .Sh DESCRIPTION

54 The

55 .Fn getlogin

56 routine

57 returns the login name of the user associated with the current session,

58 as previously set by

59 .Fn setlogin .

60 The name is normally associated with a login shell

61 at the time a session is created,

62 and is inherited by all processes descended from the login shell.

63 (This is true even if some of those processes assume another user ID,

64 for example when

65 .Xr su 1

66 is used.)

67 .Pp

68 .Fn setlogin

69 sets the login name of the user associated with the current session to

70 .Fa name .

71 This call is restricted to the super-user, and

72 is normally used only when a new session is being created on behalf

73 of the named user

74 (for example, at login time, or when a remote shell is invoked).

75 .Sh RETURN VALUES

76 If a call to

77 .Fn getlogin

78 succeeds, it returns a pointer to a null-terminated string in a static buffer.

79 If the name has not been set, it returns

80 .Dv NULL .

81 If a call to

82 .Fn setlogin

83 succeeds, a value of 0 is returned. If

84 .Fn setlogin

85 fails, a value of -1 is returned and an error code is

86 placed in the global location

87 .Va errno .

88 .Sh ERRORS

89 The following errors may be returned by these calls:

90 .Bl -tag -width Er

91 .It Bq Er EFAULT

92 The

93 .Fa name

94 parameter gave an

95 invalid address.

96 .It Bq Er EINVAL

97 The

98 .Fa name

99 parameter

100 pointed to a string that was too long.

101 Login names are limited to

102 .Dv MAXLOGNAME

103 (from

104 .Ao Pa sys/param.h Ac )

105 characters, currently 12.

106 .It Bq Er EPERM

107 The caller tried to set the login name and was not the super-user.

108 .El

109 .Sh SEE ALSO

110 .Xr setsid 2

111 .Sh BUGS

112 Login names are limited in length by

113 .Fn setlogin .

114 However, lower limits are placed on login names elsewhere in the system

115 .Pf ( Dv UT_NAMESIZE

116 in

117 .Ao Pa utmp.h Ac ) .

118 .Pp

119 In earlier versions of the system,

120 .Fn getlogin

121 failed unless the process was associated with a login terminal.

122 The current implementation (using

123 .Fn setlogin )

124 allows getlogin to succeed even when the process has no controlling terminal.

125 In earlier versions of the system, the value returned by

126 .Fn getlogin

127 could not be trusted without checking the user ID.

128 Portable programs should probably still make this check.

129 .Sh HISTORY

130 The

131 .Fn getlogin

132 function first appeared in 4.4BSD.