GETLINE(3) - man page online | library functions

Delimited string input.

GETLINE(3)                          Linux Programmer's Manual                          GETLINE(3)


getline, getdelim - delimited string input


#include <stdio.h> ssize_t getline(char **lineptr, size_t *n, FILE *stream); ssize_t getdelim(char **lineptr, size_t *n, int delim, FILE *stream); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): getline(), getdelim(): Since glibc 2.10: _POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700 Before glibc 2.10: _GNU_SOURCE


getline() reads an entire line from stream, storing the address of the buffer containing the text into *lineptr. The buffer is null-terminated and includes the newline character, if one was found. If *lineptr is set to NULL and *n is set 0 before the call, then getline() will allocate a buffer for storing the line. This buffer should be freed by the user program even if get‐ line() failed. Alternatively, before calling getline(), *lineptr can contain a pointer to a mal‐ loc(3)-allocated buffer *n bytes in size. If the buffer is not large enough to hold the line, getline() resizes it with realloc(3), updating *lineptr and *n as necessary. In either case, on a successful call, *lineptr and *n will be updated to reflect the buf‐ fer address and allocated size respectively. getdelim() works like getline(), except that a line delimiter other than newline can be specified as the delimiter argument. As with getline(), a delimiter character is not added if one was not present in the input before end of file was reached.


On success, getline() and getdelim() return the number of characters read, including the delimiter character, but not including the terminating null byte ('\0'). This value can be used to handle embedded null bytes in the line read. Both functions return -1 on failure to read a line (including end-of-file condition). In the event of an error, errno is set to indicate the cause.


EINVAL Bad arguments (n or lineptr is NULL, or stream is not valid).


For an explanation of the terms used in this section, see attributes(7). ┌──────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├──────────────────────┼───────────────┼─────────┤ │getline(), getdelim() │ Thread safety │ MT-Safe │ └──────────────────────┴───────────────┴─────────┘


Both getline() and getdelim() were originally GNU extensions. They were standardized in POSIX.1-2008.


#define _GNU_SOURCE #include <stdio.h> #include <stdlib.h> int main(void) { FILE *stream; char *line = NULL; size_t len = 0; ssize_t read; stream = fopen("/etc/motd", "r"); if (stream == NULL) exit(EXIT_FAILURE); while ((read = getline(&line, &len, stream)) != -1) { printf("Retrieved line of length %zu :\n", read); printf("%s", line); } free(line); fclose(stream); exit(EXIT_SUCCESS); }


read(2), fgets(3), fopen(3), fread(3), scanf(3)


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GNU 2015-03-29 GETLINE(3)
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getline(3) referred by fparseln(3) | gets(3) | mk-configure(7) | rpmatch(3)
refer to attributes(7) | feature_test_macros(7) | fgetc(3) | fopen(3) | fread(3) | malloc(3) | read(2) | scanf(3)