| Defined in header <stdio.h> | ||||
|---|---|---|---|---|
|
Puts the character ch back to the given file stream.
Parameters
| ch | - | character to be put back |
| stream | - | file stream to put the character back to |
Return value
On success ch is returned.
On failure EOF is returned and the given stream remains unchanged.
Example
ungetc with error checking.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 | #include <stdio.h>#include <stdlib.h> int main(void){ FILE* fp = fopen("test.txt", "w"); fputs("abc\n", fp); fclose(fp); fp = fopen("test.txt", "r"); /* Read "abc". */ /* Write "abbc". */ char ch; int ret_code; ch=fgetc(fp); /* read 'a' */ putchar(ch); ch=fgetc(fp); /* read 'b' */ putchar(ch); ret_code = ungetc(ch,fp); /* push 'b' back to input file */ /* Test whether EOF was reached. */ if (ret_code == EOF) if (ferror(fp)) { perror("ungetc()"); fprintf(stderr,"ungetc() failed in file %s at line # %d\n", __FILE__,__LINE__-6); exit(EXIT_FAILURE); } ch=fgetc(fp); /* reread 'b' */ putchar(ch); ch=fgetc(fp); /* read 'c' */ putchar(ch); return EXIT_SUCCESS;} |
Output:
1 | abbc |
References
- C11 standard (ISO/IEC 9899:2011):
- 7.21.7.10 The ungetc function (p: 334)
- C99 standard (ISO/IEC 9899:1999):
- 7.19.7.11 The ungetc function (p: 300)
- C89/C90 standard (ISO/IEC 9899:1990):
- 4.9.7.11 The ungetc function
See also
| gets a character from a file stream (function) | |
C++ documentation for ungetc | |
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