getchar()
Hi, i have a c question. My program is supposed to replace all the backspace char (hitting backspace) with \b, the tab char with \t the \ (slash) char with \\
my problem is everything works in my program except for printing backspace.
for example:
Input: asdf1234(hit tab)12(hit backspace)34( hit \ char )
Output: asdf1234\t134\\
as you can see \t and \\ are used in place of tab and \
but backspace merely deletes a char instead of just printing \b
i heard somewhere that the terminal reads and deals with backspaces before the program, could this be the reason getchar() cannot get a value when backspace is hit? I don't know if its true or not. The following code is what i wrote in responce to an exersice in k&r second edition.
heres the code:
#include
/* Write a program to copy its input to its output, replacing each tab by /t, each backspace by \b, and each backslash by \\. This makes tabs and backspaces visible in an unambiguous way. */
main()
{
int c;
while((c=getchar()) != EOF) {
if(c=='\t') {
c = c - '\t';
printf("\\t");
}
if(c=='\\') {
c = c - '\\';
printf("\\\\");
}
if(c=='\b') { //c doesn't like this code
c = c - '\b';
printf("\\b");
}
putchar(c);
}
}
Comments
-
heres the source code in a text file [file name=replacetab.txt size=489]http://www.linux.com/media/kunena/attachments/legacy/files/replacetab.txt[/file]0
-
On most systems, the backspace is ^H; however, if your terminal is configured for buffered input, the driver will intercept the ^H and do the "rubout the last character input" that you have experienced. You need to modify the behavior of the tty with either the stty command before you start your program, or within your program with the tcsetattr() function. You can turn off buffered input so that you can directly intercept the back-space that you input from the keyboard.0
-
Thanks for your reply. Yeah I kind of figured something like that, im glad I gave up on the excise or else I would still be trying it. So thanks, I guess I just wont mess with it.0
-
You can use the stty command from the shell to alter this behavior before you start your program.
stty erase 0 ; myprogram ; stty ek
This will turn off the backspace/erase actions, run your program, and then turn it back on. You can do the same thing with other special characters as well.0
Categories
- All Categories
- 175 LFX Mentorship
- 175 LFX Mentorship: Linux Kernel
- 745 Linux Foundation IT Professional Programs
- 372 Cloud Engineer IT Professional Program
- 168 Advanced Cloud Engineer IT Professional Program
- 73 DevOps IT Professional Program - Discontinued
- 3 DevOps & GitOps IT Professional Program
- 98 Cloud Native Developer IT Professional Program
- 7.6K Training Courses & Learning Paths
- AI & ML Training
- Blockchain & Decentralized Identity Training
- 1 Cloud & Containers Training
- Cybersecurity Training
- DevOps & Site-Reliability Training
- Linux Kernel Development Training
- Networking Training
- Open Source Best Practice Training
- System Administration Training
- System Engineering Training
- Web & Application Development Training
- 2 LFD103-JP クラス フォーラム
- 4 LFD210-CN Class Forum
- 764 LFD259 Class Forum
- 681 LFS101 Class Forum
- 2 LFS158-JP クラス フォーラム
- 162 LFS207 Class Forum
- 3 LFS207-DE-Klassenforum
- 4 LFS207-JP クラス フォーラム
- 61 LFS241 Class Forum
- 52 LFS242 Class Forum
- 42 LFS243 Class Forum
- 19 LFS244 Class Forum
- 4 LFS250-JP クラス フォーラム
- 166 LFS253 Class Forum
- 1.4K LFS258 Class Forum
- 792 Hardware
- 202 Drivers
- 68 I/O Devices
- 37 Monitors
- 95 Multimedia
- 173 Networking
- 91 Printers & Scanners
- 87 Storage
- 768 Linux Distributions
- 81 Debian
- 67 Fedora
- 22 Linux Mint
- 13 Mageia
- 24 openSUSE
- 150 Red Hat Enterprise
- 31 Slackware
- 13 SUSE Enterprise
- 356 Ubuntu
- 465 Linux System Administration
- 31 Cloud Computing
- 73 Command Line/Scripting
- Github systems admin projects
- 98 Linux Security
- 78 Network Management
- 101 System Management
- 46 Web Management
- 106 Mobile Computing
- 18 Android
- 73 Development
- 1.2K New to Linux
- 1K Getting Started with Linux
- 392 Off Topic
- 121 Introductions
- 181 Small Talk
- 29 Study Material
- 946 Programming and Development
- 310 Kernel Development
- 618 Software Development
- 978 Software
- 370 Applications
- 182 Command Line
- 5 Compiling/Installing
- 68 Games
- 317 Installation
- Archived
- 2 LFD140 Class Forum
Upcoming Training
-
August 20, 2018
Kubernetes Administration (LFS458)
-
August 20, 2018
Linux System Administration (LFS301)
-
August 27, 2018
Open Source Virtualization (LFS462)
-
August 27, 2018
Linux Kernel Debugging and Security (LFD440)