1SETENV(3)                  Linux Programmer's Manual                 SETENV(3)
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NAME

6       setenv - change or add an environment variable
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SYNOPSIS

9       #include <stdlib.h>
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11       int setenv(const char *name, const char *value, int overwrite);
12       int unsetenv(const char *name);
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14   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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16       setenv(), unsetenv():
17           _POSIX_C_SOURCE >= 200112L
18               || /* Glibc <= 2.19: */ _BSD_SOURCE
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DESCRIPTION

21       The  setenv()  function  adds the variable name to the environment with
22       the value value, if name does not already exist.  If name does exist in
23       the  environment,  then  its  value is changed to value if overwrite is
24       nonzero; if overwrite is zero, then the value of name  is  not  changed
25       (and setenv() returns a success status).  This function makes copies of
26       the strings pointed to by name and value (by contrast with putenv(3)).
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28       The unsetenv() function deletes the variable name from the environment.
29       If  name does not exist in the environment, then the function succeeds,
30       and the environment is unchanged.
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RETURN VALUE

33       setenv() and unsetenv() functions return zero on success, or -1 on  er‐
34       ror, with errno set to indicate the error.
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ERRORS

37       EINVAL name is NULL, points to a string of length 0, or contains an '='
38              character.
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40       ENOMEM Insufficient memory to add a new variable to the environment.
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ATTRIBUTES

43       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
44       tributes(7).
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46       ┌────────────────────────────────┬───────────────┬─────────────────────┐
47       │Interface                       │ Attribute     │ Value               │
48       ├────────────────────────────────┼───────────────┼─────────────────────┤
49       │setenv(), unsetenv()            │ Thread safety │ MT-Unsafe const:env │
50       └────────────────────────────────┴───────────────┴─────────────────────┘
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CONFORMING TO

53       POSIX.1-2001, POSIX.1-2008, 4.3BSD.
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NOTES

56       POSIX.1 does not require setenv() or unsetenv() to be reentrant.
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58       Prior to glibc 2.2.2, unsetenv() was prototyped as returning void; more
59       recent glibc versions follow the POSIX.1-compliant prototype  shown  in
60       the SYNOPSIS.
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BUGS

63       POSIX.1 specifies that if name contains an '=' character, then setenv()
64       should fail with the error EINVAL; however, versions  of  glibc  before
65       2.3.4 allowed an '=' sign in name.
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SEE ALSO

68       clearenv(3), getenv(3), putenv(3), environ(7)
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COLOPHON

71       This  page  is  part of release 5.12 of the Linux man-pages project.  A
72       description of the project, information about reporting bugs,  and  the
73       latest     version     of     this    page,    can    be    found    at
74       https://www.kernel.org/doc/man-pages/.
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78GNU                               2021-03-22                         SETENV(3)
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