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fop(1): adds more comments

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This commit is contained in:
Emma Tebibyte 2024-07-13 18:03:49 -06:00
parent c7c6ca2c60
commit e4e823a309
Signed by untrusted user: emma
GPG Key ID: 06FA419A1698C270
1 changed files with 26 additions and 13 deletions
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39
src/fop.rs
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@ -32,8 +32,8 @@ use sysexits::{ EX_DATAERR, EX_IOERR, EX_UNAVAILABLE, EX_USAGE };
fn main() {
let argv = args().collect::<Vec<String>>();
let mut d = '\u{1E}'.to_string();
let mut index_arg = 0;
let mut d = '\u{1E}'.to_string(); /* ASCII record separator */
let mut optind = 0;
let usage = format!(
"Usage: {} [-d delimiter] index command [args...]",
@ -43,10 +43,9 @@ fn main() {
while let Some(opt) = argv.getopt("d:") {
match opt.opt() {
Ok(_) => {
/* unwrap because Err(OptError::MissingArg) will be returned if
* opt.arg() is None */
/* delimiter */
d = opt.arg().unwrap();
index_arg = opt.ind();
optind = opt.ind();
},
Err(_) => {
eprintln!("{}", usage);
@ -55,38 +54,46 @@ fn main() {
};
}
let command_arg = index_arg as usize + 1;
/* index of the argv[0] for the operator command */
let command_arg = optind as usize + 1;
argv.get(command_arg).unwrap_or_else(|| {
/* argv[0] of the operator command */
let operator = argv.get(command_arg).unwrap_or_else(|| {
eprintln!("{}", usage);
exit(EX_USAGE);
});
let index = argv[index_arg].parse::<usize>().unwrap_or_else(|e| {
/* parse the specified index as a number we can use */
let index = argv[optind].parse::<usize>().unwrap_or_else(|e| {
eprintln!("{}: {}: {}", argv[0], argv[1], e);
exit(EX_DATAERR);
});
let mut buf = String::new();
let _ = stdin().read_to_string(&mut buf);
/* split the buffer by the delimiter (by default, '\u{1E}') */
let mut fields = buf.split(&d).collect::<Vec<&str>>();
/* collect arguments for the operator command */
let opts = argv
.iter()
.clone()
.skip(command_arg + 1)
.skip(command_arg + 1) /* skip the command name */
.collect::<Vec<&String>>();
let mut spawned = Command::new(argv.get(command_arg).unwrap())
.args(opts)
/* spawn the command to operate on the field */
let mut spawned = Command::new(operator)
.args(opts) /* spawn with the specified arguments */
.stdin(Stdio::piped())
.stdout(Stdio::piped())
.stdout(Stdio::piped()) /* piped stdout to handle output ourselves */
.spawn()
.unwrap_or_else( |e| {
eprintln!("{}: {}: {}", argv[0], argv[command_arg], e.strerror());
exit(EX_UNAVAILABLE);
});
/* get field we want to pipe into spawned program */
let field = fields.get(index).unwrap_or_else(|| {
eprintln!(
"{}: {}: No such index in input",
@ -96,9 +103,10 @@ fn main() {
exit(EX_DATAERR);
});
/* get the stdin of the newly spawned program and feed it the field val */
if let Some(mut child_stdin) = spawned.stdin.take() {
let _ = child_stdin.write_all(field.as_bytes());
drop(child_stdin);
drop(child_stdin); /* stay safe! drop your children! */
}
let output = spawned.wait_with_output().unwrap_or_else(|e| {
@ -106,17 +114,22 @@ fn main() {
exit(EX_IOERR);
});
/* get the output with which the original field will be replaced */
let mut replace = output.stdout.clone();
/* as long as it’s not a newline, set the replacement to the output */
if replace.pop() != Some(b'\n') { replace = output.stdout; }
/* convert the output of the program to UTF-8 */
let new_field = String::from_utf8(replace).unwrap_or_else(|e| {
eprintln!("{}: {}: {}", argv[0], argv[command_arg], e);
exit(EX_IOERR);
});
/* store the new field in the old fields vector */
fields[index] = &new_field;
/* fop it */
stdout().write_all(
fields.join(&d.to_string()).as_bytes()
).unwrap_or_else(|e| {