projects / unix-history / blame
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1 | .\" Copyright (c) 1988 The Regents of the University of California. |
| 2 | .\" All rights reserved. | |
| c80211f9 | 3 | .\" |
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4 | .\" Redistribution and use in source and binary forms are permitted |
| 5 | .\" provided that the above copyright notice and this paragraph are | |
| 6 | .\" duplicated in all such forms and that any documentation, | |
| 7 | .\" advertising materials, and other materials related to such | |
| 8 | .\" distribution and use acknowledge that the software was developed | |
| 9 | .\" by the University of California, Berkeley. The name of the | |
| 10 | .\" University may not be used to endorse or promote products derived | |
| 11 | .\" from this software without specific prior written permission. | |
| 12 | .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR | |
| 13 | .\" IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED | |
| 14 | .\" WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. | |
| 15 | .\" | |
| 5da6f084 | 16 | .\" @(#)getenv.3 6.6 (Berkeley) %G% |
| 31b20f0a | 17 | .\" |
| 500e7be1 | 18 | .TH GETENV 3 "" |
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19 | .AT 3 |
| 20 | .SH NAME | |
| 4f3c5ada | 21 | getenv, setenv, unsetenv \- manipulate environmental variables |
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22 | .SH SYNOPSIS |
| 23 | .nf | |
| 24 | .B char *getenv(name) | |
| 25 | .B char *name; | |
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26 | .PP |
| 27 | .B setenv(name, value, overwrite) | |
| 28 | .B char *name, value; | |
| 29 | .B int overwrite; | |
| 30 | .PP | |
| 31 | .B void unsetenv(name) | |
| 32 | .B char *name; | |
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33 | .fi |
| 34 | .SH DESCRIPTION | |
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35 | \fIGetenv\fP searches the environment list (see \fIenviron\fP(7)) |
| 36 | for a string of the form \fIname\fP\fB=\fP\fIvalue\fP and returns | |
| 37 | a pointer to the string \fIvalue\fP if such a string is present, | |
| 38 | and 0 (NULL) if it is not. | |
| 39 | .PP | |
| 40 | \fISetenv\fP searches the environment list as \fIgetenv\fP does; if | |
| 41 | the string \fIname\fP is not found, a string of the form | |
| 42 | \fIname\fP\fB=\fP\fIvalue\fP is added to the environment. If it is | |
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43 | found, and \fIoverwrite\fP is non-zero, its value is changed to |
| 44 | \fIvalue\fP. \fISetenv\fP returns 0 on success and -1 on failure, | |
| 45 | where failure is caused by an inability to allocate space for the | |
| 46 | environment. | |
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47 | .PP |
| 48 | \fIUnsetenv\fP removes all occurrences of the string \fIname\fP from | |
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49 | the environment. There is no library provision for completely removing |
| 50 | the current environment. It is suggested that the following code be | |
| 51 | used to do so. | |
| 52 | .PP | |
| 53 | .nf | |
| 54 | static char *envinit[1]; | |
| 55 | extern char **environ; | |
| 56 | environ = envinit; | |
| 57 | .fi | |
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58 | .PP |
| 59 | All of these routines permit, but do not require, a trailing equals | |
| 83296280 | 60 | (``='') sign on \fIname\fP or a leading equals sign on \fIvalue\fP. |
| c80211f9 | 61 | .SH SEE ALSO |
| 4f3c5ada | 62 | csh(1), sh(1), execve(2), environ(7) |
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63 | .SH BUGS |
| 64 | All information is part of the environment, so it must be copied | |
| 65 | if it is to be manipulated. |