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);
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13       int unsetenv(const char *name);
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15   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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17       setenv(), unsetenv():
18           _POSIX_C_SOURCE >= 200112L
19               || /* Glibc versions <= 2.19: */ _BSD_SOURCE
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DESCRIPTION

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

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

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

44       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
45       tributes(7).
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47       ┌──────────────┬───────────────┬─────────────────────┐
48       │Interface     │ Attribute     │ Value               │
49       ├──────────────┼───────────────┼─────────────────────┤
50       │setenv(), un‐ │ Thread safety │ MT-Unsafe const:env │
51       │setenv()      │               │                     │
52       └──────────────┴───────────────┴─────────────────────┘

CONFORMING TO

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

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

64       POSIX.1 specifies that if name contains an '=' character, then setenv()
65       should  fail  with  the error EINVAL; however, versions of glibc before
66       2.3.4 allowed an '=' sign in name.
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SEE ALSO

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

72       This page is part of release 5.10 of the Linux  man-pages  project.   A
73       description  of  the project, information about reporting bugs, and the
74       latest    version    of    this    page,    can     be     found     at
75       https://www.kernel.org/doc/man-pages/.
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79GNU                               2017-09-15                         SETENV(3)
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