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| .\" Converted for Linux, Mon Nov 29 14:24:40 1993, faith@cs.unc.edu |
| .\" Added remark on EBADF for fileno, aeb, 2001-03-22 |
| .\" |
| .TH FILENO 3 2021-03-22 "" "Linux Programmer's Manual" |
| .SH NAME |
| fileno \- obtain file descriptor of a stdio stream |
| .SH SYNOPSIS |
| .nf |
| .B #include <stdio.h> |
| .PP |
| .BI "int fileno(FILE *" stream ); |
| .fi |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR fileno (): |
| .nf |
| _POSIX_C_SOURCE |
| .fi |
| .SH DESCRIPTION |
| .PP |
| The function |
| .BR fileno () |
| examines the argument |
| .I stream |
| and returns the integer file descriptor used to implement this stream. |
| The file descriptor is still owned by |
| .I stream |
| and will be closed when |
| .BR fclose (3) |
| is called. |
| Duplicate the file descriptor with |
| .BR dup (2) |
| before passing it to code that might close it. |
| .PP |
| For the nonlocking counterpart, see |
| .BR unlocked_stdio (3). |
| .SH RETURN VALUE |
| On success, |
| .BR fileno () |
| returns the file descriptor associated with |
| .IR stream . |
| On failure, \-1 is returned and |
| .I errno |
| is set to indicate the error. |
| .SH ERRORS |
| .TP |
| .B EBADF |
| .I stream |
| is not associated with a file. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR fileno () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| The function |
| .BR fileno () |
| conforms to POSIX.1-2001 and POSIX.1-2008. |
| .SH SEE ALSO |
| .BR open (2), |
| .BR fdopen (3), |
| .BR stdio (3), |
| .BR unlocked_stdio (3) |