#Bash 的 cd 命令
1cd [-L|-P] [DIRECTORY] 2
功能
切换工作目录。
类型
Bash 内置命令。
参数
OPTION选项：-L- 逻辑路径；在跟踪符号链接之前解析..（默认）-P- 物理路径；在跟踪符号链接之后解析..
DIRECTORY- 要切换到的目录路径；省略表示切换到用户目录，-表示切换到上次的工作目录
#示例
基本示例
1$ pwd # 查看当前路径 2/home/user/primers 3$ cd bash # 相对路径 4$ pwd 5/home/user/primers/bash 6$ cd - # 切换回之前的目录 7$ pwd 8/home/user/primers 9$ cd /etc # 绝对路径 10$ pwd 11/etc 12
符号链接
1$ pwd # 查看当前路径 2/home/user/primers 3$ ln -s /usr/lib lib # 创建符号链接 4$ cd lib # 进入 lib 5$ pwd 6/home/user/primers/bash/lib 7$ cd .. # 返回上级目录 8$ cd -P lib # 进入 lib，跟踪符号链接 9$ pwd 10/usr/lib 11
#相关命令
| 命令 | 说明 |
|---|---|
| pushd | 将当前工作目录压入栈顶，并切换工作目录 |
| popd | 将目录栈的栈顶移除，并切换工作目录 |
| dirs | 查看当前工作目录和目录栈 |
#推荐阅读
#手册
显示
1CD(1P) POSIX Programmer's Manual CD(1P) 2PROLOG top 3 This manual page is part of the POSIX Programmer's Manual. The 4 Linux implementation of this interface may differ (consult the 5 corresponding Linux manual page for details of Linux behavior), or 6 the interface may not be implemented on Linux. 7NAME top 8 cd — change the working directory 9SYNOPSIS top 10 cd [-L|-P] [directory] 11 12 cd - 13DESCRIPTION top 14 The cd utility shall change the working directory of the current 15 shell execution environment (see Section 2.12, Shell Execution 16 Environment) by executing the following steps in sequence. (In the 17 following steps, the symbol curpath represents an intermediate 18 value used to simplify the description of the algorithm used by 19 cd. There is no requirement that curpath be made visible to the 20 application.) 21 22 1. If no directory operand is given and the HOME environment 23 variable is empty or undefined, the default behavior is 24 implementation-defined and no further steps shall be taken. 25 26 2. If no directory operand is given and the HOME environment 27 variable is set to a non-empty value, the cd utility shall 28 behave as if the directory named in the HOME environment 29 variable was specified as the directory operand. 30 31 3. If the directory operand begins with a <slash> character, set 32 curpath to the operand and proceed to step 7. 33 34 4. If the first component of the directory operand is dot or dot- 35 dot, proceed to step 6. 36 37 5. Starting with the first pathname in the <colon>-separated 38 pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if 39 the pathname is non-null, test if the concatenation of that 40 pathname, a <slash> character if that pathname did not end 41 with a <slash> character, and the directory operand names a 42 directory. If the pathname is null, test if the concatenation 43 of dot, a <slash> character, and the operand names a 44 directory. In either case, if the resulting string names an 45 existing directory, set curpath to that string and proceed to 46 step 7. Otherwise, repeat this step with the next pathname in 47 CDPATH until all pathnames have been tested. 48 49 6. Set curpath to the directory operand. 50 51 7. If the -P option is in effect, proceed to step 10. If curpath 52 does not begin with a <slash> character, set curpath to the 53 string formed by the concatenation of the value of PWD, a 54 <slash> character if the value of PWD did not end with a 55 <slash> character, and curpath. 56 57 8. The curpath value shall then be converted to canonical form as 58 follows, considering each component from beginning to end, in 59 sequence: 60 61 a. Dot components and any <slash> characters that separate 62 them from the next component shall be deleted. 63 64 b. For each dot-dot component, if there is a preceding 65 component and it is neither root nor dot-dot, then: 66 67 i. If the preceding component does not refer (in the 68 context of pathname resolution with symbolic links 69 followed) to a directory, then the cd utility shall 70 display an appropriate error message and no further 71 steps shall be taken. 72 73 ii. The preceding component, all <slash> characters 74 separating the preceding component from dot-dot, dot- 75 dot, and all <slash> characters separating dot-dot 76 from the following component (if any) shall be 77 deleted. 78 79 c. An implementation may further simplify curpath by removing 80 any trailing <slash> characters that are not also leading 81 <slash> characters, replacing multiple non-leading 82 consecutive <slash> characters with a single <slash>, and 83 replacing three or more leading <slash> characters with a 84 single <slash>. If, as a result of this canonicalization, 85 the curpath variable is null, no further steps shall be 86 taken. 87 88 9. If curpath is longer than {PATH_MAX} bytes (including the 89 terminating null) and the directory operand was not longer 90 than {PATH_MAX} bytes (including the terminating null), then 91 curpath shall be converted from an absolute pathname to an 92 equivalent relative pathname if possible. This conversion 93 shall always be considered possible if the value of PWD, with 94 a trailing <slash> added if it does not already have one, is 95 an initial substring of curpath. Whether or not it is 96 considered possible under other circumstances is unspecified. 97 Implementations may also apply this conversion if curpath is 98 not longer than {PATH_MAX} bytes or the directory operand was 99 longer than {PATH_MAX} bytes. 100 101 10. The cd utility shall then perform actions equivalent to the 102 chdir() function called with curpath as the path argument. If 103 these actions fail for any reason, the cd utility shall 104 display an appropriate error message and the remainder of this 105 step shall not be executed. If the -P option is not in effect, 106 the PWD environment variable shall be set to the value that 107 curpath had on entry to step 9 (i.e., before conversion to a 108 relative pathname). If the -P option is in effect, the PWD 109 environment variable shall be set to the string that would be 110 output by pwd -P. If there is insufficient permission on the 111 new directory, or on any parent of that directory, to 112 determine the current working directory, the value of the PWD 113 environment variable is unspecified. 114 115 If, during the execution of the above steps, the PWD environment 116 variable is set, the OLDPWD environment variable shall also be set 117 to the value of the old working directory (that is the current 118 working directory immediately prior to the call to cd). 119OPTIONS top 120 The cd utility shall conform to the Base Definitions volume of 121 POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines. 122 123 The following options shall be supported by the implementation: 124 125 -L Handle the operand dot-dot logically; symbolic link 126 components shall not be resolved before dot-dot 127 components are processed (see steps 8. and 9. in the 128 DESCRIPTION). 129 130 -P Handle the operand dot-dot physically; symbolic link 131 components shall be resolved before dot-dot components 132 are processed (see step 7. in the DESCRIPTION). 133 134 If both -L and -P options are specified, the last of these options 135 shall be used and all others ignored. If neither -L nor -P is 136 specified, the operand shall be handled dot-dot logically; see the 137 DESCRIPTION. 138OPERANDS top 139 The following operands shall be supported: 140 141 directory An absolute or relative pathname of the directory that 142 shall become the new working directory. The 143 interpretation of a relative pathname by cd depends on 144 the -L option and the CDPATH and PWD environment 145 variables. If directory is an empty string, the results 146 are unspecified. 147 148 - When a <hyphen-minus> is used as the operand, this shall 149 be equivalent to the command: 150 151 cd "$OLDPWD" && pwd 152 153 which changes to the previous working directory and then 154 writes its name. 155STDIN top 156 Not used. 157INPUT FILES top 158 None. 159ENVIRONMENT VARIABLES top 160 The following environment variables shall affect the execution of 161 cd: 162 163 CDPATH A <colon>-separated list of pathnames that refer to 164 directories. The cd utility shall use this list in its 165 attempt to change the directory, as described in the 166 DESCRIPTION. An empty string in place of a directory 167 pathname represents the current directory. If CDPATH is 168 not set, it shall be treated as if it were an empty 169 string. 170 171 HOME The name of the directory, used when no directory 172 operand is specified. 173 174 LANG Provide a default value for the internationalization 175 variables that are unset or null. (See the Base 176 Definitions volume of POSIX.1‐2017, Section 8.2, 177 Internationalization Variables for the precedence of 178 internationalization variables used to determine the 179 values of locale categories.) 180 181 LC_ALL If set to a non-empty string value, override the values 182 of all the other internationalization variables. 183 184 LC_CTYPE Determine the locale for the interpretation of sequences 185 of bytes of text data as characters (for example, 186 single-byte as opposed to multi-byte characters in 187 arguments). 188 189 LC_MESSAGES 190 Determine the locale that should be used to affect the 191 format and contents of diagnostic messages written to 192 standard error. 193 194 NLSPATH Determine the location of message catalogs for the 195 processing of LC_MESSAGES. 196 197 OLDPWD A pathname of the previous working directory, used by cd 198 -. 199 200 PWD This variable shall be set as specified in the 201 DESCRIPTION. If an application sets or unsets the value 202 of PWD, the behavior of cd is unspecified. 203ASYNCHRONOUS EVENTS top 204 Default. 205STDOUT top 206 If a non-empty directory name from CDPATH is used, or if cd - is 207 used, an absolute pathname of the new working directory shall be 208 written to the standard output as follows: 209 210 "%s\n", <new directory> 211 212 Otherwise, there shall be no output. 213STDERR top 214 The standard error shall be used only for diagnostic messages. 215OUTPUT FILES top 216 None. 217EXTENDED DESCRIPTION top 218 None. 219EXIT STATUS top 220 The following exit values shall be returned: 221 222 0 The directory was successfully changed. 223 224 >0 An error occurred. 225CONSEQUENCES OF ERRORS top 226 The working directory shall remain unchanged. 227 228 The following sections are informative. 229APPLICATION USAGE top 230 Since cd affects the current shell execution environment, it is 231 always provided as a shell regular built-in. If it is called in a 232 subshell or separate utility execution environment, such as one of 233 the following: 234 235 (cd /tmp) 236 nohup cd 237 find . -exec cd {} \; 238 239 it does not affect the working directory of the caller's 240 environment. 241 242 The user must have execute (search) permission in directory in 243 order to change to it. 244EXAMPLES top 245 The following template can be used to perform processing in the 246 directory specified by location and end up in the current working 247 directory in use before the first cd command was issued: 248 249 cd location 250 if [ $? -ne 0 ] 251 then 252 print error message 253 exit 1 254 fi 255 ... do whatever is desired as long as the OLDPWD environment variable 256 is not modified 257 cd - 258RATIONALE top 259 The use of the CDPATH was introduced in the System V shell. Its 260 use is analogous to the use of the PATH variable in the shell. The 261 BSD C shell used a shell parameter cdpath for this purpose. 262 263 A common extension when HOME is undefined is to get the login 264 directory from the user database for the invoking user. This does 265 not occur on System V implementations. 266 267 Some historical shells, such as the KornShell, took special 268 actions when the directory name contained a dot-dot component, 269 selecting the logical parent of the directory, rather than the 270 actual parent directory; that is, it moved up one level toward the 271 '/' in the pathname, remembering what the user typed, rather than 272 performing the equivalent of: 273 274 chdir(".."); 275 276 In such a shell, the following commands would not necessarily 277 produce equivalent output for all directories: 278 279 cd .. && ls ls .. 280 281 This behavior is now the default. It is not consistent with the 282 definition of dot-dot in most historical practice; that is, while 283 this behavior has been optionally available in the KornShell, 284 other shells have historically not supported this functionality. 285 The logical pathname is stored in the PWD environment variable 286 when the cd utility completes and this value is used to construct 287 the next directory name if cd is invoked with the -L option. 288FUTURE DIRECTIONS top 289 None. 290SEE ALSO top 291 Section 2.12, Shell Execution Environment, pwd(1p) 292 293 The Base Definitions volume of POSIX.1‐2017, Chapter 8, 294 Environment Variables, Section 12.2, Utility Syntax Guidelines 295 296 The System Interfaces volume of POSIX.1‐2017, chdir(3p) 297COPYRIGHT top 298 Portions of this text are reprinted and reproduced in electronic 299 form from IEEE Std 1003.1-2017, Standard for Information 300 Technology -- Portable Operating System Interface (POSIX), The 301 Open Group Base Specifications Issue 7, 2018 Edition, Copyright 302 (C) 2018 by the Institute of Electrical and Electronics Engineers, 303 Inc and The Open Group. In the event of any discrepancy between 304 this version and the original IEEE and The Open Group Standard, 305 the original IEEE and The Open Group Standard is the referee 306 document. The original Standard can be obtained online at 307 http://www.opengroup.org/unix/online.html . 308 309 Any typographical or formatting errors that appear in this page 310 are most likely to have been introduced during the conversion of 311 the source files to man page format. To report such errors, see 312 https://www.kernel.org/doc/man-pages/reporting_bugs.html . 313 314IEEE/The Open Group 2017 CD(1P) 315
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