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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |ATTRIBUTES |STANDARDS |HISTORY |EXAMPLES |SEE ALSO |COLOPHON | |
getline(3) Library Functions Manualgetline(3)getline, getdelim - delimited string input
Standard C library (libc,-lc)
#include <stdio.h>ssize_t getline(char **restrictlineptr, size_t *restrictn,FILE *restrictstream);ssize_t getdelim(char **restrictlineptr, size_t *restrictn,intdelim, FILE *restrictstream); Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):getline(),getdelim(): Since glibc 2.10: _POSIX_C_SOURCE >= 200809L Before glibc 2.10: _GNU_SOURCE
getline() reads an entire line fromstream, 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 before the call, thengetline() will allocate a buffer for storing the line. This buffer should be freed by the user program even ifgetline() failed. Alternatively, before callinggetline(),*lineptr can contain a pointer to amalloc(3)-allocated buffer*n bytes in size. If the buffer is not large enough to hold the line,getline() resizes it withrealloc(3), updating*lineptr and*n as necessary. In either case, on a successful call,*lineptr and*n will be updated to reflect the buffer address and allocated size respectively.getdelim() works likegetline(), except that a line delimiter other than newline can be specified as thedelimiter argument. As withgetline(), a delimiter character is not added if one was not present in the input before end of file was reached.
On success,getline() andgetdelim() 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. At end of file, both functions return -1 with the file stream end- of-file indicator set. On error, both functions return -1 with the file stream error indicator set, anderrno is set to indicate the error. If*lineptr was set to NULL before the call, then the buffer should be freed by the user program even on failure.EINVALBad arguments (n orlineptr is NULL, orstream is not valid).ENOMEMAllocation or reallocation of the line buffer failed.
For an explanation of the terms used in this section, seeattributes(7). ┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface│Attribute│Value│ ├──────────────────────────────────────┼───────────────┼─────────┤ │getline(),getdelim() │ Thread safety │ MT-Safe │ └──────────────────────────────────────┴───────────────┴─────────┘
POSIX.1-2008.
GNU, POSIX.1-2008.
#define _GNU_SOURCE #include <stdio.h> #include <stdlib.h> int main(int argc, char *argv[]) { FILE *stream; char *line = NULL; size_t size = 0; ssize_t nread; if (argc != 2) { fprintf(stderr, "Usage: %s <file>\n", argv[0]); exit(EXIT_FAILURE); } stream = fopen(argv[1], "r"); if (stream == NULL) { perror("fopen"); exit(EXIT_FAILURE); } while ((nread = getline(&line, &size, stream)) != -1) { printf("Retrieved line of length %zd:\n", nread); fwrite(line, nread, 1, stdout); } free(line); fclose(stream); exit(EXIT_SUCCESS); }read(2),fgets(3),fopen(3),fread(3),scanf(3)
This page is part of theman-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17getline(3)Pages that refer to this page:fgetc(3), gets(3), rpmatch(3), scanf(3)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |